Hi all. I have a JTS that has run very rich since we have owned it. I mentioned this early on and also that it ran cold and was told about the dodgy thermostat issue. So I have changed that, could have sworn it was running closer to 90 degrees but a few months later it doesn't seem to get above 70 degrees or so and takes a long time to warm up. So I think the new stat is knackerd or the gauge is reading wrong. I wanted to buy a laser thermometer to get a proper read of the running temp but figured a new thermostat cost about the same so have just ordered a new one. If the old one is still ok I will have a spare at least. Also I noticed the rocker cover is leaking oil into at least one of the plug holes which I have read can be a problem so one of those is also on order. Also I haven't looked at the air filter yet (bad I know) so one is on order. Apart from a new thermostat I have read the O2 sensors could be on the way out, dirty MAF or even leaky injectors. Air filter is easy and will be the next thing I do but failing that what do you guys reckon should be my next port of call? I don't really think it's leaky injectors as I reckon this would be more of an issue at low revs or on start up. Our issue seems to be from about 3000 rpm and up- drive it even semi hard and you see a huge black smoke plume behind, but no noticeable smoke below that. At the price injectors go for I don't want to touch them until last!
I have read about a fair few rich running JTS's but seemingly for a lot of different reasons. I want to keep the car so don't want to let it do any (more?) damage- I can't imagine its that good for it.
Another thing, I know these cars are OBD2 compatible- would a scan gauge tell me anything of use? It's not giving me engine lights ATM.
Cheers
Josh
I did a bit of investigating today. I found a hose from the rocker cover to behind the throttle body cracked. I replaced that but it didn't seem to make much difference- maybe a smoother idle. Next I pulled out the air filter- what a crap design to access something that should be easy! As i thought it might be it was filthy so I fitted the AFM back in without it. Then I let it warm up and then held it at 2000 rpm and watched the temp gauge to see what it got up to, if I could tell when the thermostat opened and at what gauge temp the fan cuts in. It took its time but slowly rose to 90 degrees where the fan cut in- so I can tell the gauge is right and the fan works. I then took it for a drive and it quickly settled back to about 70 and rose to maybe 80 at slower speeds. It is much less smokey than before, seemingly better the closer it gets to 90 degrees.
So my verdict is that seeing the thermostat is supposed to open at 82 degrees and I have worked out the gauge is correct that the thermostat is at least slightly open- crap because it's a new one. I think my smokey problem was a combination of a blocked filter and stuffed thermostat. So as in the previous post I have ordered a new thermostat, I went for an Aussie Tridon this time, rather than the european one I ordered last time. I was going to order a new filter but I decided to modify the airbox and fit a pod filter I already had. This basically involved cutting most of the box out but retained the top and bottom so it mounds as it should. I'm really happy with the results- it revs much more cleanly and sounds great, with a really throaty induction roar but not droney at cruising speed. Hopefully this new thermostat can make it run at the right temp and we'll be very happy.
Cheers
Josh, check posts by our resident thermostat expert Colcol for a definitive account of the crapness of thermostats fitted to 156s, and their tendency to pack up anytime from new.
Thanks mate, Colin is the one who first let me know of the thermostat issue. Im pretty sure he told me that about them too.
Cheers
Hey again guys. I finally got around to fitting the new thermostat and yes, the old (new) one was buggered. It now rises quickly up to and holds 90 degrees and does seem to run a little better but still smokes like a chimney. Give it a boot full and watch the black smoke plume in the mirror from about 4000 rpm and up. Looking at the plugs though, they don't seem too bad- light brown colour with small black deposits around the base of the thread. So it seems it is running the right mixture most of the time, just not when I have described. So what's next, O2 sensors? Also is the ECU one of the learning type, ie might it take a while to reconfigure to the new running temp or something?
Also our car uses a LOT of oil, which I know is a JTS thing. Could this be the smoke plume? I always thought oil smoke to be blue in colour, where this looks very black.
Cheers
Josh
You need to get a compression test done to see if the rings have gone. JTS cars are known for having fragile rings and they crack with age.
Black smoke is a rich AFR, i.e. unburnt carbon.
To the best of my understanding;
When running on a light throttle the ECU should be trimming the AFR according to the signal it gets from the O2 sensors (i.e. 'closed loop' running). When you floor it the ECU will ignore the 02 sensors and run the engine according to unchanging pre-programmed maps (i.e. 'open loop'). The ECU also operates in a (different) open loop mode when the 02 sensors are still too cold to work properly, i.e. for the first minute or so of driving (a bit longer if the engine is left to idle from cold). This is why the sensors have an electrically driven 'self heating' function, i.e. to get them up to working temperature more quickly than the exhaust heat alone can do.
Open loop AFRs are fairly rich (i.e. cold temperature and wide throttle opening). When the engine is cold this is because the ECU assumes a rich AFR is needed for the engine to run acceptably (even when the 02 sensors start to work and the ECU goes into open loop mode but the coolant temp is still below X°, the open loop AFR will still be fairly rich because the ECU assumes a rich AFR is needed due to the the still relatively cool cylinder temperature, i.e. it's harder to ignite and adequately burn a relatively lean mixture in a relatively cool cylinder). This is why you get poor fuel economy when the thermostat sticks open and the coolant fails to reach X°, the AFR is still in open loop cold mode.
At throttle openings approaching WOT (wide open throttle) the open loop AFR mode will be quite rich because the engine requires a fairly rich AFR both to produce the power needed for acceleration (or maintaining a high speed), and because a rich AFR burns cooler than a leaner AFR. This cooler burn helps prevent 'detonation' (which is damaging), but also means that the spark plugs, piston crowns and the exhaust valves are in less danger of overheating when the engine is approaching or at max power output.
So, if the engine black smokes with light throttle openings then it could be an issue with the 02 sensors, or one of them. If it smokes with heavy throttle then it might be something else, maybe injectors, or an injector. If say one injector is not flowing enough fuel (i.e. partially blocked) then the resulting lean condition can (counter intuitively) cause a rich AFR in other cylinders.
I'm not sure of the JTS set up, but for example the TS engine uses two O2 sensors (the pre-cat sensors, which are the ones the ECU pays attention to for controlling AFR), each serving to read O2 content from two cylinders. If one cylinder is running lean then the sensor will detect an overall lean AFR in the combined exhaust gasses from both cylinders, and will then increase pulse width for both injectors (i.e. open the injectors for a longer time) until it 'sees' the reading it 'wants' to see from that sensor. This will result in one injector over fueling and the other still probably under-fueling, but the over fueled cylinder will still be producing black sooty smoke because it can't burn all the fuel injected into it (this will also have an adverse affect on power, so the driver will open the throttle more...).
This assumes that the ECU can control the pulse width of each injector individually (or at least the two associated with each sensor, independent of the two injectors associated with the other sensor), which I'm not certain of. If it can't then the result may be more or less the same, the ECU will increase injector pulse width for all cylinders until it sees an overall O2 content that it 'wants' to see. The result will be some cylinders over fueled and at least one under fueled, and even though overall O2 content in the exhaust gasses may be within parameters, there will be unburnt carbon blackening the exhaust gasses, loss of power, and worsened fuel economy.
I would expect that if the ECU 'sees' a significant disparity between the readings from both O2 sensors (as might happen if say one sensor is faulty) that it would 'know' something was wrong and at least throw a CEL warning. But it might not.
I've had two injectors totally fail on my TS engine (not at the same time). They stuck completely open, and just hosed raw fuel into their cylinder. Of course this resulted in lots of black smoke and very poor running. I expect it also caused the ECU to substantially lean off at least one other injector (the other one associated with the sensor), and maybe all three other injectors. I doubt this has happened with your engine, the symptoms are quite severe, much worse than you describe.
It might be worthwhile to have your injectors checked and cleaned. It might be worthwhile to have the O2 sensor outputs checked. Accretions from burnt oil can affect the O2 sensors...
Regards,
John.
The ECU will generally not adjust the mixture from the O2 readings beyond a certain amount, which should be nowhere near enough to cause 'plumes of smoke'. Given the smoke starts appearing at around 3-4k rpm, and its a JTS I'd be wondering whether the camshaft variator is actually working, or whether the cams have any lobes left on them.
Of course, it could also be that 3-4k is where there is enough volume and heat moving through the cylinder to clear the build up of fuel or oil.
How much oil is it actually using - a 'lot' doesn't really tell us much...
Before doing anything, get a simple compression test done, it will tell you if you have problems with the rings/valves.
As the smoke seems to be coming on at above 4000 rpm the next two usual suspects are valve guide seals or a bad intake manifold seal around the Variator Oil Galleries. If you are leaking oil at the manifold gasket though you should notice #1 & #2 spark plugs suffering from more oil fouling than the others.
Also check all the vacuum hoses going to and from the main air intake hose and the PCV crankcase hose that is just behind the throttle body.
Baz
Yes, but Josh is saying that the smoke is quite black, not grey or bluish. Of course this doesn't preclude that there might not be oil smoke mixed up in the blackness of what sounds very much like smoke created by an overly rich AFR.
I agree that the ECU shouldn't normally enrich so much as to cause "plumes" of smoke. However, the ECU on our Saab was certainly able to massively over fuel the engine when the O2 sensor died, to the point that the spark plugs sooted up so much that the engine wouldn't start. Once I managed to get the engine going (after pulling and cleaning the plugs), it would run very badly and produced lots of black smoke. It would run fine if you planted the boot, but as soon as you backed off it was rough as guts with little poke (can't drive with WOT all the time...). I replaced the sensor, problem sorted...
This issue with the Saab O2 sensor was a bit of a learning curve for me, took me quite a while to diagnose the problem (after nearly all other possibilities had been investigated and ruled out). One thing I learned was that an O2 sensor can be utterly defunct and the ECU won't necessarily detect it, just continues to trust the signal it's getting and blithely dumps more and more fuel into the engine...
Regards,
John.
Thanks guys, definitely some food for thought. How would I tell if the variator is working or not? There has never been any rattle from it but that doesn't mean that it is working. It doesn't have a "V-Tec" style step in power delivery but I always assumed this was due to it being continuously variable and not intrusive. Can the variator be felt kicking in normally?
Oil use wise it will go from the full to the low mark on the dip stick within a week or two of driving, about 500km.
Cheers
How would I tell if the variator is working or not? There has never been any rattle from it but that doesn't mean that it is working.
At idle, disconnect the variator solenoid electrical plug. If the variator is operable then when you disconnect the solenoid it will stop working (i.e. oil pressure will stop being fed to the variator), and the idle will get rough. At least this is what happens with my TS engine, i.e. disconnecting the variator solenoid causes a very marked deterioration in idle quality, which makes me think that the variator must activated at lower rpm, so must be 'inactive' at higher rpm.
It doesn't have a "V-Tec" style step in power delivery but I always assumed this was due to it being continuously variable and not intrusive. Can the variator be felt kicking in normally?
My understanding is that the the variator is either 'on' or 'off', it doesn't have a progression in the way it works (at least with the TS engine, though I expect the JTS variator is similar).
I don't know about the JTS (never driven one), but the TS (at least mine) has a point at about 3500 rpm where the power picks up noticeably. I assume this is when the ECU cuts power to the variator solenoid and it stops working, which is when the inlet camshaft advances (this is just an assumption that may not be correct, the pick up in power could easily be explained by other engine parameters). When the inlet timing is advanced there is also a resulting increase in 'overlap' of the inlet and exhaust cam timing, which is a 'good thing' for high rpm power, but causes rough running and poor power at low rpm / idle.
Oddly, the variator purportedly stops advancing the inlet timing above about 5000 rpm, which seems exceedingly strange to me. I would have though this would impair power above 5000 rpm. It would also make the engine less rev happy (unlike a V-Tec where the change in timing is carried all the way to the red line). Maybe it's supposed to, perhaps to discourage revving the engine above this speed...???
I have read somewhere (a few places I think) that the solenoid is not activated at idle / low rpm and becomes activated at higher rpm (at differing rpm depending on the particular version of the engine). However my experience suggests that it is opposite to this, i.e. activated at lower rpm / idle, and becomes deactivated at higher rpm. If the variator was not electrically activated at low rpm, then why would disconnecting its solenoid cause the idle to become rough??
So, unless I'm missing something, discounting what it does over 5000 rpm, it seems to me that rather than the variator activating and advancing the inlet timing at higher rpm, it instead is activated at lower rpm and retards the inlet timing when it's activated. If so then the variator deactivates to allow the inlet timing to advance at higher rpm, as opposed to being activated to allow the timing to advance...
Oil use wise it will go from the full to the low mark on the dip stick within a week or two of driving, about 500km.
Cheers
That could be enough to coat the O2 senors in gunk. This could easily cause the sensor to work badly. If the gunk is thick enough to impair 02 from being detected in the exhaust gasses, then the sensor will generate a low voltage which the ECU will interpret as a lean AFR, and will then enrich until it 'sees' a signal voltage that it 'wants' to see. The problem is that the actual AFR may be already a lot richer than the ECU 'thinks' it is, so a very rich actual AFR will be the result.
Regards,
John.
OPERATION IN CLOSED STAGE
When the closed stage is required (idle speed and maximum power zone), the solenoid is de-energized, so the slide valve in the base mount of the solenoid prevents the oil from reaching the variator.
In this case the timing of the inlet valves remains unchanged (closed).
OPERATION IN OPEN STAGE
When the open stage is required (medium rpm with high torque). The solenoid is energized, thus opening the slide valve allowing oil to enter the Variator and forcing it to rotate clockwise which transmits rotation to the camshaft, thus varying by 25° engine the timing of the inlet valves.
The Variator operation is disabled below 2500-3000rpm, the idea being to give better economy at more "conservative" driving styles. Hence the reason why 2.0 TS & JTS seem doughy and unresponsive below 3000rpm, drop a gear, put the boot in and it kicks in and "away we go!"
There is an old Alfa Romeo saying, "Fun starts at 3000!" ;)
From Wikipedia -
Alfa Romeo system
In 1970, Fiat patented a variable valve timing system, however it was Alfa Romeo who first applied VVT in 1980 to the long-established Twin Cam engine used in the Alfa Romeo Spider. The technique derives from work carried in the 1970s by Ing. Giampaolo Garcea and in Italian the device is termed variatore di fase. The Alfa Romeo Twin Spark engine, introduced in the 1987 Alfa Romeo 75, also uses variable valve timing.
The Alfa system varies the phase (not the duration) of the cam timing and operates on the inlet camshaft.
Alfa Romeo's variator is a cylindrical chamber that contains a pressure chamber and piston along with helical splines. Engine oil pressure, moves the internal piston which rotates slightly due to the helical splines and advances the inlet valve timing by 25 degrees. Oil flow to the variator is controlled by a solenoid valve. When engine speed reaches a certain speed, normally 1500-2000 rpm in the Twin Spark application, the solenoid energises, causing pressurised oil to be directed through the inlet camshaft into the variator. The inlet camshaft position is advanced 25 degrees, thus increasing valve overlap. It remains in this advanced state until about 5000 rpm when the solenoid switches off, and the variator piston returns the valve timing to its natural state. The variable timing increases the engine's mid-range flexibility and reduces emissions. Exact changeover points depend on version. It is notable that this relatively early system only has two settings: unchanged and fully advanced.
Thanks guys.
The car goes really well and revs freely so I reckon the variator is working. Gunked up O2 sensors seems to be a more logical path to me. I know one pair are active and one pair are just something to do with the cats, but don't know which. If I were to replace a pair which would it be, or should i do all? Even O2 sensors seems a bit fishy though as the rich running is only up higher in the revs, not all the time. Also I would have thought if the sensors were not working right it would throw some sort of code.
Honestly the car goes great, I just want to know what's causing all the smoke (and soot on the bumper!) and how much better it might go at the right mixture.
Cheers
It's got nothing to do as to whether the variator is working or not, it has to do with is it leaking oil from galleries that run through the inlet manifold due to a poor sealing gasket.
And if you have soot all over your bumper it is NOT from faulty O2 sensors, true they probably are not working too well but they are not the cause of the problem, they are collateral damage.
As no smoke is emitting at less than 4000rpm (from your supplied information) it is most likely worn Valve Stem Seals, damaged rings or oil leaking from the Variator galleries due to a poor sealing inlet manifold.
The fact that your car uses oil like a Destroyer on D-Day doing Smoke Screen Duty is ALSO indicative of one of these errors.
Thanks Bazz. I take it a new inlet manifold would be a pretty easy job, and valve guide seals could be done when i do the timing belt. As far as compression is concerned, what values should I expect, and is there a special way to do it on this car due to the electronic throttle body? Number one plug has been wet with oil but Im sure this was due to a leaky cam cover gasket, which i replaced the other day.
Im still confused as to why the smoke seems very black when i always thought oil smoke was supposed to be blue. Though it makes sense it it's oil smoke due to how much oil it uses.
Realistically, how much chance is there of it being a simpler fix like the manifold gasket or stem seals, rather than bad rings? I guess a comp test will confirm it.
Cheers
OPERATION IN CLOSED STAGE
When the closed stage is required (idle speed and maximum power zone), the solenoid is de-energized, so the slide valve in the base mount of the solenoid prevents the oil from reaching the variator.
In this case the timing of the inlet valves remains unchanged (closed).
OPERATION IN OPEN STAGE
When the open stage is required (medium rpm with high torque). The solenoid is energized, thus opening the slide valve allowing oil to enter the Variator and forcing it to rotate clockwise which transmits rotation to the camshaft, thus varying by 25° engine the timing of the inlet valves.
The Variator operation is disabled below 2500-3000rpm, the idea being to give better economy at more "conservative" driving styles. Hence the reason why 2.0 TS & JTS seem doughy and unresponsive below 3000rpm, drop a gear, put the boot in and it kicks in and "away we go!"
There is an old Alfa Romeo saying, "Fun starts at 3000!" ;)
Baz, you are correct, and my memory is faulty. Off the top of my head I was recalling (from nearly a year ago) the idle becoming a lot worse when I disconnected the solenoid (very 'hunty', as is typical with a lot of valve overlap). But thinking back more carefully what I actually did was to artificially energise the solenoid at idle (testing). It was this that caused the idle to worsen, i.e. energising the solenoid at idle, which means the variator must be inactive at idle / low rpm.
Considering this, I do wonder why the variator tends to rattle for a couple of seconds at start up, until general oil pressure builds and it stops rattling. Surely if the variator is not activated (at idle / low rpm, and again above 5000 rpm) because it is isolated from oil pressure because the solenoid is not 'on', then the variator should not rattle at start up? Yet it does, and only stops when general pressure builds, which implies that even when the solenoid is 'de-energised' the variator must still be seeing at least some pressure at idle / low rpm. Doesn't make sense to me. Confused...
Is it possible that the solenoid is staged, i.e. with at least two 'settings', one allowing X pressure to reach the variator (to prevent rattling), and another allowing X+ pressure to reach it, enough to overcome resistance and advance inlet timing?
Yes, the TS engine is quite doughy below 3000 rpm. At least with my car it also behaves differently when performing heel/toe down shifts. The engine response from a throttle 'blip' is far less predictable below 3000 rpm, making it much harder to achieve clean heel/toe shifts at lower rpm. It would be interesting to see what happens with this if the solenoid were to be artificially switched 'on' 'permanently'...
Regards,
John.
Quote from: josh18 on April 05, 2017, 12:15:16 PM
Thanks Bazz. I take it a new inlet manifold would be a pretty easy job, and valve guide seals could be done when i do the timing belt. As far as compression is concerned, what values should I expect, and is there a special way to do it on this car due to the electronic throttle body? Number one plug has been wet with oil but Im sure this was due to a leaky cam cover gasket, which i replaced the other day.
Im still confused as to why the smoke seems very black when i always thought oil smoke was supposed to be blue. Though it makes sense it it's oil smoke due to how much oil it uses.
Realistically, how much chance is there of it being a simpler fix like the manifold gasket or stem seals, rather than bad rings? I guess a comp test will confirm it.
Cheers
Josh,
Replacing valve guides and seals is a head off job.
I doubt the inlet manifold has anything to do with your problem (been wrong before...). It wouldn't hurt to check that all the manifold nuts are tight (or even still there...).
It's not a bad idea to check compression, keeping in mind that an engine with good compression can still leak oil past the rings (in some cases the extra oil around the compression rings can actually improve compression test numbers). Ideally a compression check should be done with the butterfly wide open, as this will maximise compression numbers measured. However, the most important thing with compression testing isn't the maximum numbers (unless they are all quite low), but the relative numbers cylinder to cylinder. They should all be fairly close to each other. Since checking compression with a closed butterfly will affect all cylinders equally (restricting airflow into the cylinders), it won't make much difference to the relative numbers you'll see (though the absolute numbers will be somewhat lower).
Having said this, unless I'm missing something you could do the compression check with the injector wires disconnected and the throttle pedal held to the floor, which will prevent fuel being injected during the testing. If fuel is injected it will be expelled from the spark plug orifices (all plugs should be out for compression testing so the engine can spin freely), which is at least a fire hazard (don't ask me how I know...).
I'm not quite with Baz on this. He seems convinced your smoke is oil smoke, and while much of it probably is considering your oil consumption, I think the blackness does also point to a rich AFR. My experience is that oil smoke is bluish gray, quite a different colour to fuel smoke. I think Baz is quite right to be concerned at your engines' oil consumption, it does seem quite excessive to me.
At some stage soon I think you'll need to be thinking about the points where oil can enter the cylinders, i.e. rings, valve guides and seals. Another entry point is though crankcase breathers, you might want to have a look at at the hose where the crankcase gasses are vented into the inlet manifold. If this is very oily then this may be where much of the oil is getting in. If it is don't get too exited about any easy fix, oil usually spews from this hose because of excessive crankcase pressure, which is caused by compression and particularly combustion pressures escaping past the compression rings into the crankcase...
(edit to add; there is a 'fix' of sorts for this, crankcase pressure can be vented into a catch tank (to stop oil spillage) rather than into the manifold, but, this is illegal to do...)
I'd still be having a look at the 02 sensors. The pre cat ones are used for measuring 02, the post cat ones are so the ECU can monitor the main cat function, and have no influence on AFR (at least with most engines as I understand it, I don't know the JTS, but I doubt it's different). The problem is that replacing 02 sensors in an engine that is burning a lot of oil
might fix the problem in the short term, but continued oil burning may well wreck the new sensors fairly quickly...
From what you say you don't really know if your #1 plug is oily because of oil entering the cylinder, or simply that oil flowed over it when you pulled it out (from the oil in the plug well). You need to clean the plug well of oil, then drive the car for a while before having another look at the plug (hopefully the leak is slow enough that the well won't just fill with oil again).
Regards,
John.
Ok, by telling me that #1 spark plug is oily you have just confirmed that is most likely oil leaking through the inlet manifold galleries. And for you and John, here is a photo of what happens when it leaks.
Also this is the easiest to check, just take the inlet manifold off.
Oil going down the plug tube from leaking camshaft cover wont foul the plug as the plug is sealed against the head, its just the tube that fills with oil.
If I am wrong and its all clean, then it is most likely valve seals. And John, if it was from being OVER FUELLED, why are all the other spark plugs nice and light brown? If it is being over fuelled to the point of leaving oily residue all over the rear bumper I think you'd find the plugs to be in similar condition.
(http://www.alfaowner.com/Forum/attachment.php?attachmentid=61215&stc=1&thumb=1&d=1480605040)
Baz
It seems Josh can't say whether the plug was oily before he pulled it, because of the oil sitting in the plug well that may have just run over the plug when it was extracted. This needs to be clarified.
You have a point, if the engine is consistently running rich then the plugs should show it. But, if the engine only runs rich at wider throttle openings then they might not, because the majority of running might be lean enough to clear the plug of a sooty build up. It's still possible that #1 cylinder is indeed running rich, enough to cause black smoke. If so then the other cylinders are most likely running at least somewhat lean due to the one very rich cylinder affecting overall 02 content in the exhaust gasses and so corrupting the signal to the ECU.
If only one cylinder is running rich (if it is), then I think there would definitely be a problem with the injector to that cylinder, i.e failing to fully close, or maybe sticky, so it can't respond fast enough to the required pulse width (this would keep it effectively open longer than it should be), though, I would expect this to affect AFR at all throttle openings.
If excessive oil is getting into #1 (quite possible), it would create grey smoke. If the cylinder is very rich then any grey smoke can be hidden by the black smoke. If the valve seals are toast, then I would expect to see more smoke at start up after the car had been sitting for some time (enough time for oil to drain past the seal, down the guide and into the cylinder, or to sit on top of a closed valve). This is a classic symptom of worn seals / guides, as is a puff of oil smoke as you get on throttle after the engine has been on the over run with a closed throttle (very high manifold vacuum 'sucking' oil into the ports through the stem / guide clearances, then burnt as soon as the throttle is opened). After a short while running the oil smoke from worn stem seals tends to diminish. If on the other hand the engine smokes more consistently then it's more likely to be oil leaking past the piston rings.
The oil in the plug well isn't good, but not a big deal, just messy. It won't cause a loss of spark at the plug because oil is a very poor conductor of electricity. My Accord used to leak a heap of oil into the plug wells (before I fixed it), and I can't say I ever noticed any misfires. It is indeed conceivable for an 'oil bath' to prevent a misfire, say by effectively insulating an eroded hole in the plug lead where a spark would otherwise be free to jump to the side of the plug tube...
Regards,
John.
Here is a guide for doing a compression test. Values for your car should be between 200 - 250psi
http://www.freeasestudyguides.com/compression-test-wet.html
Don't forget to check the Crankcase High Speed Breather Valve (PCV Valve), its the one going from the top back right of your Cam Cover to just behind the Throttle Body. It can get clogged up which will cause high oil usage too. So check that first, it's the easiest. Just be careful removing the plastic valve cover behind the Throttle Body, old plastic is brittle. Give the valve cover a good clean as well as the little golf tee valve inside, make sure the spring is not broken.
Then compression check, to disable fuel and ignition, remove the corresponding relays in front of the battery.
Then check for variator duct leak in the manifold gasket.
These are the easiest in order.
Baz
Thanks guys, you both have some really good points and info. I think like John said, the oil on number one plug came from the oil in the pug well saturating the plug when i took it out. I have replaced the gasket so it should be dry in there when i check it again so i will have a better idea of where oil if any is from.
The way john described worn valve seals was pretty much my understanding of it too- smoke on acceleration after the over run due to high vacuum.
Thanks Bazz for the tip on the breathers etc. I will re read all the posts and go through all the easier things this weekend.
There is a pretty good chance I am seeing blue smoke in the mirror and mistaking it as black, seeing the plugs are not fouled (I have a lucas injected Triumph as my toy, so I know what fouled plugs look like), but as John said it only seems rich some of the time. Fuel economy is still pretty good though too.
Cheers guys
Baz is right to suggest checking the PCV. Any blockage in the breather system means that crankcase pressure can't easily vent, so the pressure rises and rises to the point that one of the easiest pathways to relieve the pressure is into the cylinder void past the piston rings. This happens when the cylinder pressures are low, mostly on the induction stroke (when cylinder pressures are actually negative), and oil is carried with the crankcase gasses into the cylinder.
Another symptom often associated with a blocked breather is a multitude of small oil leaks, because the pressure can be high enough to force oil past any weak gasket or other seals (might explain a leaky cam cover gasket...?).
High crankcase pressure also reduces performance appreciably, because it takes energy for the pistons to descend against the higher than usual crankcase pressures. This is a debatable point, because it can be argued that the pressure also pushes against the underside of the simultaneously ascending pistons, so it's a zero sum game, i.e. no net increase in power required to move the pistons. What I do know from experience with blocked breathers on a couple of cars I have owned, declogging resulted in a quite noticeable improvement in performance...
Regards,
John.
Forgot to mention that high crankcase pressures can also force oil from the case into the cylinders via the valve guides. I suspect less will tend to flow through worn guides / seals than will flow past worn rings, all else being equal.
More thoughts on crankcase breather systems, as per my understanding of them;
Most systems use two hoses between the case and the induction system. One hose (A) is connected to the induction at some point between the butterfly valve and the ports (i.e. somewhere on the inlet manifold), and is exposed to high vacuum at small throttle openings, and lesser vacuum at larger openings. The PCV is part of this circuit, and restricts hose A gas flow into the manifold at higher manifold vacuum, and increasing flow as manifold vacuum decreases. The idea is that the 'air leak' into the manifold created by hose A is always flowing a more or less consistent quantity of gasses, which can be adequately accounted for by the ECU or the carburettor jetting (i.e. more relative pressure through a smaller orifice at high manifold vacuum, less relative pressure through a larger orifice at lower vacuum, hopefully amounting to a similar gas quantity flowed in the differing conditions). If the PCV were not there, then this would be an uncontrolled air leak.
Hose A 'sucks' fairly hard at small throttle openings (idle / low rpm cruise), when blow-by gas production is low and at relatively low pressure in the case. At larger throttle openings the manifold vacuum reduces and blow-by and case pressure increase, but a lesser %age of the total pressure and gas escapes through hose A because of the lower manifold vacuum and the restriction created by the PCV (even fully open it's a fairly small valve area relative to the quantity of blow-by gasses being created).
The second hose (B) is connected to the induction pipe before the throttle body (or carburettor), and never sees the degree of vacuum that hose A sees at small throttle openings. At idle / low rpm, hose B allows the crankcase to actually be ventilated with filtered fresh air, not just for the pressure to be relieved (hose A sucks gas from the crankcase as hose B allows fresh air to flow in, replacing harmful gasses, including water vapour). This helps to scavenge harmful gaseous chemicals from the crankcase (products of combustion, many of which are acidic), which otherwise would be absorbed into the oil, and increase the rate of oil contamination.
When throttle opening is high, cylinder pressures increase dramatically, and thus so does the blow-by gas (I think both max out at the max torque rpm, when cylinder pressures are greatest). A lesser %age of the crankcase pressure / gas now escapes through hose A, but due to the increase in blow-by gasses the flow through hose B reverses, so now much more blow-by gas flows though hose B, which is then 'sucked' into the engine through the throttle body (or carburettor). This is aided by the decrease in manifold vacuum at larger throttle openings, and by the concurrent increase in vacuum before the butterfly (where hose B connects).
Normally not much oil will be carried with the blow-by gas through hose B (or hose A for that matter). However, if blow-by is quite substantially more than it should be, then quite a lot of oil can be carried through both hoses with the gasses. If an engine tends to get a filthy throttle body, then this is likely to be the problem, i.e. excessive blow-by. The worst example of this I've experienced was the Fiat Twin Cam engine in the Nota Sportsman I used to own (google it if you're wondering). The engine generally ran well, but really it needed new rings, blow-by was excessive.
If this car was driven at about 110kmh for a long stretch then blow-by pressure could steadily increase until oil would spray from hose B into the air filter canister, get sucked in through the carbs and create a smokescreen behind the car. Then, at lower speeds the car would run rough for a while until the plugs cleared, and if you had to come to a stop it could stall and be somewhat reluctant to restart.
Regards,
John.
Ok guys, compression test done and all were around 215 to 220 dry and all about 250 to 250 wet (three squirts of oil).
PCV hoses seem to be clear but I couldn't find the golf tee valve in the cam cover. It looks to be just a baffle setup, glued and bolted in. It didnt seem like it would come out without breaking it. I dont have any other leaks anywhere though so I doubt it is blocked and pressurizing the crank case. I am going to try running with the PCV hose off though (into a can) and see if it runs different and if it is expelling anything. That pipe was cracked previously and it didn't run any different so I think it should run ok with out it (am I wrong?).
I did notice though that while I thought the cams are in good nick, they are stuffed. I'll post pics later but one of quite a few lobe pairs are worn pretty severely. At first it looked like it was meant to be like that as it is smooth but they are all different. One exhaust lobe is almost gone! i don't know if this could have anything to do with my smoke issues but it needs to be fixed.
I haven't looked at the manifold gasket yet but will put a pic up of the week old plugs. They all look pretty similar, some slightly darker than the others and all black around just the base.
So going by my comression results is it safe to say that the rings might be ok and it's valve guide seals or is it too hard to tell without a strip down? I'm prepared to either fix or change the head (timing belt needs doing soon anyway) but am not up for a rebuild. Also am I looking at stuffed bearings with all the cam metal floating around in the oil? It has always seemed particle free, hopefully the filter has done it's job!
To tell you the truth we have been thinking about selling this car on but everything else we look at is so boring! So I am trying to decide whether or not to put some more money into it and keep it.
Cheers, pics later
So I put some long hoses onto the cam cover vent and wrapped them up in a white rag. I blocked off the respective lines to the TB.
I noticed the vent puts out a bit of pressure so I guess there is a bit of blow by the rings but all engines do this, I don't know how much though. So on my drive It still blows smoke, but on inspection of the rag afterwards it was still clean, so I don't think a blocked PCV or venting oil into the inlet is an issue.
So that leaves me with rings, valve stem seals or the manifold gasket leak.
So from my limited knowledge, if it was rings I would have thought the compression would be down more, valve guides like John said, would be more likely after idling or after decelerating in gear. So next port of call will be to inspect that gasket. Looking at the set up, it looks like a pretty painful job to get the manifold off- is there an easy way?
One thing I noticed on this drive is that the smoke seems to start as the engine makes a slight change in tone, maybe the variator kicking in or out? It seems to be around 5000 rpm, so when it disengages?
Here are some pics of the plugs and cams. Looking back at the plugs, number 1 is definitely darker. Let me know what you think.
Cheers
pics
Haven't read the whole thread, so excuse me if I have said things others have said previously.
Plug no.1 definately is darker. Also if you have a look at the washer on the plug itself, it is covered in oil. One of my V6 does this and I'm 99% sure it's because of the valve stem seals. However, as you mentioned, it should blow blue/white smoke, not black.
Have you tried a good old Italian tune up? (A good thrashing, I mean a REALLY GOOD thrashing). You will be surprised as to how much better the car will run afterwards.
Also, I would HIGHLY recommend to check out the Coolant Temp Sensor and its wiring, I have just spent the last 6 months tracking down rich running myself and after changing everything, it turned out to the the coolant temp sensor connector.
To test it out, pull off the plug while the car is running. It should make the computer think the car is very cold (or hot, I don't quite remember) and in doing this it will over fuel (or under fuel) to compensate. You should hear a difference in idle, if not I would investigate it further.
Hope this helps, Andrew.
Thanks Andrew.
I had thought about coolant temp sensor but assumed it worked as the gauge works, but I don't know if it uses the same wiring or not. Or even if it uses the same sensor!
It's a strange issue though as it only seems to over fuel (or whatever the smoke is) above 4-5000 revs. Seems fine the rest of the time.
The plugs look just a bit sooty to me rather than oily, though it's hard to really tell from photos. One is a bit darker on the outer electrode, but not hugely. It's the porcelain colour that is more indicative, and those all look rather similar, and reasonably OK.
Your compression numbers seem healthy, suspiciously high even on the 'dry' test (oily rings can give a higher psi on a compression test). I'd expect numbers under 200 psi, though the JTS static compression ratio is fairly high, so maybe it's fine.
I'd be surprised if your problem has to do with a leaky manifold gasket. This would normally induce a lean condition, at least in the cylinder most affected. It would also tend to cause a poor idle.
Here's a trick to roughly test how much 'suction' you're getting from the inlet manifold side of the breather. Take off the oil filler cap while the engine is idling. Hold your hand just above the orifice, and you'll feel a pulsating air movement (you can take your hand away now).
Next, take a sheet of paper and slowly lower it onto the filler orifice. As the paper gets near the orifice it will at first be blown upward by the air pulsations, but as it gets very close it should suddenly get 'sucked' onto the orifice and stay there. It is being sucked onto the orifice by the low pressure created by the manifold vacuum. If not then you may have an issue, either the breather isn't working properly or the amount of blow-by gasses are too great for the breather to cope with.
Even though the pulsations make it feel (i.e. with the hand) like there is a lot of pressure in the crankcase, it's an illusion. With the cap off, blow-by gas comes out, air goes in, the fact that the paper gets sucked onto the orifice once it's close enough demonstrates that the air going in exceeds the gas coming out. The pulsating air from within the crankcase isn't caused by the blow-by gasses, but by the motion of the pistons moving up and down, moving gas rather violently as they do so (all engines do this, more noticeably the fewer cylinders there are, so with say a V12 it's likely to be less pronounced).
Now, with the paper sucked on, if you rev the engine the manifold vacuum will reduce and the blow-by will increase, and the paper will be blown off the filler orifice. This doesn't really tell you much, other than demonstrate the principal.
If that's not of much help, I hope it's at least somewhat interesting...
Regards,
John.
Thanks John, yeah I think all my tell tale signs at least say rich running, but the oil is going somewhere. With the manifold, looking at how close the variator gallery seems to be to number one I could see how oil could get in but not outside air. I have read of the issue now in a few places. By all accounts it looks like the manifold is a prick to get off with the head on.
I have ordered an OBDII cable and will buy myself a copy of MES. Seems like I am just guessing now where this setup might help me do some proper diagnosis. I also read that an ECU reset can help a lot. Im also going to try and give it a decarbon with one of the upper cylinder cleaners similar to seafoam. I keep hearing good things about this, particularly on JTS's.
I was going to buy a set of pre-cat O2 sensors but I will wait until my diagnostic stuff arrives to see what the mixture is actually doing to save possibly wasting a lot of money.
As for compression results they are in the range suggested by Bazz so Im happy with that at least. I dont know if good compression means no iol leakage from the rings but i think it's a good sign at least.
Cheers
I've never done it, nor had it done, but I think you could probably put the car on a dyno and do an exhaust gas analysis, to see how rich it actually is under varying throttle / loads...
Regards,
John.
Hi Josh,
Wise move to invest in some diagnostic gear. It'll take a lot of the guess work out of the equation if you can talk to the ECU and get an idea of the injector duty cycle.
Not unusual to richen up the mixture a bit at high rpms. That plus a bit of oil geting into the inlet tract and mixing with the spray from the injectors could explain the black / sooty smoke. Its sort of combusting with the fuel however because you have too much hydrocarbon at the time of ignition its too rich and ends up as soot.
All things being equal, a direct injection engine will be more efficient than a similar port injected engine. However the mixture produced by a direct injection / JTS is not as homogenous as the earlier port injected engines and soot is the result.
Blue (or heaven forbid) white smoke is usually a sign of oil vapourising as opposed to oxidizing.
Quote from: josh18 on April 09, 2017, 11:18:07 AM
As for compression results they are in the range suggested by Bazz so Im happy with that at least. I dont know if good compression means no iol leakage from the rings but i think it's a good sign at least.
Cheers
Did you READ ANY of the link I gave you on how to a compression test?????
The results of what you posted tell you that the rings ARE shot. If they were in good condition there should be barely any difference from dry to wet readings. When doing a compression test if you get low and varying readings and then add oil and all the readings rise and become uniform then it is a direct indication of worn rings.
Also the PVC valve - the golf tee valve is in the little plastic cylinder at the end of the hose that connects to the variable inlet manifold just behind the Throttle Body.
Baz
Owner
On the Spot Alfa - When your Alfa puts you on the spot, we're there on the spot with you.
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8 Hansen Court
Capalaba 4157
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I'd have to agree, and to a degree, disagree. I agree that the rings aren't in the best shape, but "shot" is debatable.
In my experience a wet compression test will always give a significantly higher number than the same cylinder when tested dry (well, it always has for me, though I can't recall numbers off the top of my head and I haven't done any compression testing for a long time). The commonly accepted benchmark seems to be that a wet test should make no more than about 10% higher psi (or whatever unit) for the rings to be considered fully acceptable.
Assuming so, then 10% of 227.73 (psi) = 22.73, so 227.3 + 22.73 = 250.03. So, with 250 as the wet benchmark we should be seeing about 228 psi as the fully acceptable dry compression number. The worst dry number on this engine is 215, the best 220, so the compression isn't the best, but I've seen worse wet / dry ratio in engines that still ran quite acceptably and burnt reasonably little oil. Of course if compression is down to any degree then this will affect power output to whatever degree, but if you can live with that, at least until it gets worse, and it will...
Of course this doesn't preclude any particular engine with similar numbers to this one from burning oil. The compression only has to do with the compression rings, and it's the oil scraper rings that keep too much oil from getting to the compression rings. If too much oil reaches the compression rings due to poor oil control rings, then the compression rings can 'aquaplane' on the oil, allowing oil to pass the compression rings into the cylinder.
Even if the rings are actually allowing too much oil into the cylinders, the rings themselves may still be OK. It's quite common for rings to get stuck in the ring grooves due to varnish build up and other muck, in effect gluing the rings into the grooves. If this happens the rings lose the capacity to push against the cylinder walls, and compression drops. Sometimes just cleaning the grooves and rings can work wonders. Pity it's still such a big job to get at them...
I think this is likely to be what products such as Seafoam, Auto-RX, and others largely do, i.e. dissolve deposits in the ring packs to free them up and improve compression. This is assuming such products actually do work, I've never tired them myself. Over a long enough period of time, high detergent oils might do something similar. Diesel oils are highly detergent, as are the better quality synthetics. Note that diesel oils often have a lot of zinc content, and zinc can poison catalytic converters, which could be a problem for engines already burning a fair bit of oil.
Regards,
John.
I give in, I quit !
Sorry Baz, I have done compression testing before and thought like John that there is always going to be a difference between wet and dry compression readings. It's not like the rings totally seal in normal use anyway. At 220 psi this put the readings well withing the range you suggested, and way higher than your average readings on a normal car. TBH I also give up as I think the car has now done a rod bearing (happened during my "Italian tune up" so my fault). At about 5500rpm the car let out what sounded like a bad pinking, coincided exactly with a plume of black smoke out the back. I backed off immediately but I guess too late. Upon driving home it now has a rattle (sounds more top endy) that goes away under load at low revs (not there at idle) but is pretty bad as the load comes off. Pulling number 4 coil out while running silences it, and from what I can read this is how to diagnose a rod knock. Seeing that it's not there at idle I am thinking it might not be too far gone and I will take the sump off to have a look and look at doing big end shells if the crank is not scored. Either that or a broken piston, or some sort of lifter issue? But I dont think it would run right with a broken piston.
This car seems to have a multitude of issues all happening at once, including the worn out cams and I reckon if and when i fix this issue then it will just be a matter of time before the next issue.
We love the car but I think it is more of a tinkerers car rather than a missus's run about.
Cheers for all your help guys
Not having much luck Josh...
Pulling a plug lead (or in this case a coil) helps diagnose which bearing might be bad, not really whether a noise is actually coming from a bearing (though usually it would be considered the likely cause of a regular 'knocking').
What confuses me about your symptom is that you say it's not there when the engine is under load. But, under load is when I would most be expecting to hear a knock from a bad big end bearing. Heard it many times, audible knocking even on light throttle opening, but worse at wider throttle opening (and worst at peak torque rpm), but that goes away when the throttle is closed such as on the overun and at idle. I'm not saying that a bearing isn't bad, but if so just surprised it's not louder when the engine is working harder, and is happening when the engine isn't working harder.
You also say that it sounds like a rattle and is "top endy", but a bad big end tends to sound like it's coming from the bowels of the engine, and is a regular 'knocking' noise that changes frequency with rpm. I'm not convinced that it might not be, as you suggest, something more like a broken piston, maybe.
Regards,
John.
Well I would suggest that the engine needs a rebuild all round to be honest. If you have spun a big end bearing, be careful when you drain the oil, siphon it out of the container and look for small balls/particles of white metal, same in the bottom of the sump. These are parts of big end bearing that come adrift when they fail and the definite tell tale of a done bottom bearing.
And while your there, get the head off, change the cams and valve stem seals as well as the rings. Also the inlet manifold gasket and you should be golden. Nuthin to it! ::)
;D
Hey guys, I have pulled the sump off and yes it was number 4 big end bearing worn out. It is down to the copper but not through it, and the crank journal looks fine so I reckon I got lucky. I was looking to put a new set of shells in it and sell it on but I really like the car! We have decided to get my wife a much more sensible Subaru Liberty wagon and I will look at doing a rebuild of sorts on the Alfa in my own time.
My plan is to remove the head and inspect the bores, if they are not too worn deglaze them and fit new rings and try and find a set of good second had cams. I would also do the timing belt etc at the same time. I need to look at getting the injectors refurbed at the same time if it's possible.
Has anyone had any luck with regards to oil consumption by fitting new rings without deglazing? I really want to leave the block in the car.
I'll give you a ring Baz
Cheers
Grrr, just inquired about some second hand cams and found out they are almost 400 each. With that, and a timing belt/ water pump kit injectors etc I think it's gonna be just too much, especially considering the dubious bottom end. I don't really know where to go with it now, I like the car but I definitely don't want to throw thousands at it.
Well, not a huge surprise that it did turn out to be the big end bearing. I was trying to be upbeat in the hope it might not be...
$400 each for S/H cams? It's not a Ferrari for fucks sake. Have you considered a complete second hand engine? A quick search found this from A-Twins in Sydney, for $900 (plus freight) with a 3 month warranty from a car that had done 122,000 km:
http://www.ebay.com.au/itm/ALFA-ROMEO-156-GT-GTV-SPIDER-2-0L-JTS-ENGINE-97-10-/132113780760?hash=item1ec2985018:g:t1MAAOSwOgdYqiXO
A more in depth search might do better?
Regards,
John.
Was about to make the same suggestion
http://www.ebay.com.au/itm/ALFA-ROMEO-156-JTS-2-0-LITRE-MOTOR-FIT-SPIDER-GTV-GT-EXCELENT-CONDITION-/281275400634?hash=item417d5201ba:g:kK0AAOxy4fVTEAet (http://www.ebay.com.au/itm/ALFA-ROMEO-156-JTS-2-0-LITRE-MOTOR-FIT-SPIDER-GTV-GT-EXCELENT-CONDITION-/281275400634?hash=item417d5201ba:g:kK0AAOxy4fVTEAet)
Thanks guys, that's definitely cheaper than the parts I was looking to fit to mine, by quite a margin. But it's at higher k's than mine, and at a wreckers. I reckon there's a pretty good chance it has all the same issues as mine too.
I think at this stage I am just going to do the big end shells and see how it goes. Then I will either decide to sell it or if it goes alright for a while make a call on doing the rest. Timing belt is due in 10,000 km so that would give me long enough to see if it's gonna live or not.
I measured up the suspect journal today and there is no difference between it and the good journals and looking at the specs for standard shells, withing tolerance. So at this stage it looks like it will live on.
Bazz if you're on here could you please let me know that supplier we talked about.
Cheers
Josh
These guys have the shells -
http://www.precisionintl.com.au/Default.aspx
Baz
Thanks Baz I'll give em a call
I've had generally very happy dealing with A-Twins, albeit in person, would recommend them to walk-in customers who know what they want and are past tyre kicking. That said, Dean has the patience of a saint!
Well I got my bearings from Precision from Melbourne to Darwin in less than a week which is great. I finished putting it all back together last night and took it for a tentative spin around the block. From first start the engine is much quieter, not just than before the knock but since we've had it! So i guess those big ends were all on their way out. Actually I found upon disassembly that big end three was almost as bad as four, but again no marks on the crank. Today I dropped the oil and put a new filter on and took it for a 60km drive. It goes really well and doesn't seem to knock at all. I've been quite gentle with it so far but it's definitely fixed it.
As far as the job, the only tricky bit was getting the sump back on- I had to do a dry run without sealant to work out how to hold the sump up enough to bolt the oil pick up to the block but still allow me to get my arms in there! Once i worked it out it wasn't too bad.
So fingers crossed, it looks like I saved myself from an almost blown up engine for less than $200 in the end.
Thanks to you Baz and others who have helped me out along the way.
Cheers
Josh
Glad to be of service.