Alfa Romeo Owners Club of Australia Forum

Technical => 932 Series (156, GTV, Spider, 147, GT, and 166) => Topic started by: poohbah on February 15, 2020, 12:13:38 PM

Title: rough idle 156 V6
Post by: poohbah on February 15, 2020, 12:13:38 PM
Apologies if this has been discussed previously (I couldn't find anything specific), but I am just looking for pointers.

My '99 156 V6 Q-auto has been running perfectly (major service 2 months ago including belt/pump change ... $$$$). But yesterday, after being in stop-start traffic for about an hour, and sitting stationary at a traffic light  it started idling slightly roughly.

Normally it idles very evenly, sitting bang on the 800-900 rpm mark, but it just became a bit lumpy, dropping down to 600-700rpm. Under load and driving normally all seems normal. It also seemed to be only if the transmission is in gear - when I shifted it to neutral it idled normally again.

On the drive home from work, it was generally similar, though maybe a little less pronounced - a little rough on idle, but fine when driving.

No problem starting and not running hot. Initial check under bonnet while running showed no obvious issues, vacuum leaks, loose leads etc, though on listening closely, it sounded like a faint set of "electric" clicks (maybe 3-5) would occur every now and then (possible misfire, coil packs?)

It seems pretty minor, but you soon get to know when something doesn't feel exactly right. Haven't driven yet today, so no idea if it is one of those weird temporary bugs that sometimes just disappear.

Title: Re: rough idle 156 V6
Post by: bazzbazz on February 15, 2020, 12:40:40 PM
Have you scanned it with diagnostics yet?
Title: Re: rough idle 156 V6
Post by: poohbah on February 15, 2020, 12:46:12 PM
No bazz, I don't have a scanner. No warning lights on dash or anything.

Title: Re: rough idle 156 V6
Post by: bonno on February 15, 2020, 12:51:15 PM
Hi Poohbah
Further to BazzBazz comment, it sounds like it could be a coil pack is on its way out or a faulty spark plug. I assume the NO engine light when running normal, however did you notice it light up when the rough idle occurred. If this occurs then to identify which coil pack or spark plug is at fault please refer to the following link on a similar issue I had with my 156 JTS and how I diagnosed the problem using a cheap hand held diagnostic scanner.
http://www.alfaclubvic.org.au/forum/index.php?topic=2380.msg108161#msg108161

Title: Re: rough idle 156 V6
Post by: poohbah on February 15, 2020, 01:04:26 PM
Cheers Bonno - all the warning lights come on briefly an as normal when you start her up, then go off. No warning light at all while running. I just started her and had another close look, and its as reported before. Still lumpy when in gear but idling, and intermittent electric click coming from near the first two connections/plugs on the left front side of engine. (circled - can't tell which)
Title: Re: rough idle 156 V6
Post by: poohbah on February 15, 2020, 01:19:13 PM
So possible injector fault, given that's where the click is coming from?
Title: Re: rough idle 156 V6 UPDATE
Post by: poohbah on February 15, 2020, 02:31:20 PM
Well, that's weird.

Poked and prodded around the connectors to the first two injectors a little bit, and replaced the insulation tape you can see in the pic. (The tape doesn't appear to do anything of note other than tidy things up a bit - certainly no exposed wiring or anything like that. And the tape has been there since I've owned the car - so plus 4 years).

Maybe a coincidence, but all now appears normal. No rough idle, in gear or neutral, and no intermittent click.

I guess it could be a wire/connector on the way out, which my poking jiggled back into a better contact position.

Will see how it goes, and whether it resurfaces. I'm planning to drop into the workshop when I get back from interstate in a couple of weeks to see about fitting a replacement AC compressor I bought, so will mention it then.



Title: Re: rough idle 156 V6
Post by: bazzbazz on February 16, 2020, 12:01:37 AM
Just so you know, that loose wire you have going round the left side (as in the photo) of the coil cover is supposed to go under the cover and through a hole at the bottom of the cover.

Nothing to do with your issue or its solution, just like to be tidy and do things the way they are supposed to be.

Yes, I know, picky, picky, picky.  ::)
Title: Re: rough idle 156 V6
Post by: poohbah on February 16, 2020, 12:26:54 AM
It actually now looks like this.

Anyway, main thing is that it all still seems to be working properly. Bazz, could the (currently-absent) intermittent clicking have been an injector firing erratically?
Title: Re: rough idle 156 V6
Post by: bazzbazz on February 16, 2020, 11:40:19 AM
The clicking would more likely been the zapping sound of a coil shorting out.
Title: Re: rough idle 156 V6
Post by: poohbah on February 16, 2020, 12:05:40 PM
odd that it stopped then.
Title: Re: rough idle 156 V6
Post by: bonno on February 16, 2020, 12:09:42 PM
The fault only occurs when engine has been running hot or in stop start traffic. Need to replicate same condition to see if rough idle returns.
Title: Re: rough idle 156 V6
Post by: sportiva on February 16, 2020, 12:21:03 PM
poobah
It wouldn't hurt to buy a tin of contact and circuit board cleaner and give all the different connectors a clean. My JTS had for about six months an intermitant missfire under load at about 2500 revs the check engine light would come on then after 10 or 20 seconds would go out I connected my OBD scanner and it had a missfire cylinder 2 code, so I changed plugs and swapped out another good coil and it made no difference. Then the other day the hose from the thermostat to the heater matrix split and sprayed hot coolant over everything under the bonnet. two days later I fixed the hose then degreased the engine bay to clean off the now white calcified coolant and as a precaution I cleaned all the sensor connectors the two main loom connectors and also the ECU and cat connectors. The end result a clean and tidy engine bay and no more #2 missfire the car has never run better.

Cheers sportiva
Title: Re: rough idle 156 V6
Post by: poohbah on February 16, 2020, 09:21:59 PM
cheers fellas, and good tip sportiva.

I will see how she runs in peak hour tomorrow, though it was actually misbehaving from a cold start on the return drive home the day it started and on the weekend before I prodded and poked around the injector connectors. Since then no issues during a couple of 30 min runs, though admittedly I haven't been stuck in traffic for any extended period.
Title: Re: rough idle 156 V6
Post by: Beatle on February 17, 2020, 09:26:23 PM
If you intend washing down the engine, remove the coil packs first.  Water will get into the sparkplug tubes so best to pull it all apart beforehand to make it easier to degrease, clean and de-water.

My V6 has a distinct erratic hard miss at idle, but last time I filled with 98 in lieu of the usual 95 and it's made a distinct difference to the idle.  Can't say I've noticed any change in performance off idle though.
Title: Re: rough idle 156 V6
Post by: bazzbazz on February 17, 2020, 10:51:00 PM
If you intend washing down the engine, remove the coil packs first.  Water will get into the sparkplug tubes so best to pull it all apart beforehand to make it easier to degrease, clean and de-water.

Or cover the top of the camshaft covers with plastic & tape and then do that area individually by hand. Just a thought.
Title: Re: rough idle 156 V6
Post by: poohbah on February 17, 2020, 10:55:51 PM
The good news is that had two full runs today in peak hour, 50 min each way, hot weather. No missing or rough idling all is good, and behaving 100% correctly.

Noooo Beatle - I have no intention of squirting water anywhere near the inside of the engine bay. That would be tempting fate ...

Seriously though, the engine bay is actually pretty spick and span, so no desperate need.

As an aside, I always use 98 RON - no idea if it makes any difference.
Title: Re: rough idle 156 V6
Post by: bazzbazz on February 18, 2020, 11:28:14 AM
As an aside, I always use 98 RON - no idea if it makes any difference.

Burns hotter.  ;)
Title: Re: rough idle 156 V6
Post by: poohbah on February 18, 2020, 07:56:27 PM
And longer Bazz - took the fireys 4 goes to extinguish...
Title: Re: rough idle 156 V6
Post by: Beatle on February 18, 2020, 11:22:02 PM
And longer Bazz - took the fireys 4 goes to extinguish...

I don't know if I should laugh or cry at that ........
Title: Re: rough idle 156 V6
Post by: bazzbazz on February 19, 2020, 12:21:00 AM
You wanna cry, hey Pooh, show him the photos.  :'(

 ;D
Title: Re: rough idle 156 V6
Post by: poohbah on February 21, 2020, 01:43:42 PM
 :'(
Title: Re: rough idle 156 V6
Post by: martym00se72 on February 21, 2020, 04:50:00 PM
Ouch! Did you have a fire extinguisher on board?
Title: Re: rough idle 156 V6
Post by: poohbah on February 21, 2020, 05:58:47 PM
Not back then, this was my first 156 which caught fire in 2015.

So the first thing I did when I bought both my subsequent Alfas was get a fire extinguisher.

Interesting thing I learned from the fireys was that such car fires are actually a pretty common occurrence and happen to most makes, particularly as electronics have become more complex.

Nowadays emergency responders also face the extra challenge of dealing with crashed/burning hybrid/electric vehicles (can't extinguish H/EV fires using normal retardants and they can deliver fatal shocks after a crash).
Title: Re: rough idle 156 V6
Post by: sportiva on February 21, 2020, 06:56:31 PM
Sometimes they do this.
https://www.whichcar.com.au/car-news/firefighters-drown-bmw-i8-to-put-out-electrical-fire
Title: Re: rough idle 156 V6
Post by: poohbah on February 22, 2020, 06:41:17 PM
Quote
Our Dutch firey friends utilised a clever system to fight electrical fires, though. A flatbed truck equipped with a crane and a large container of water was dispatched

So, that would mean in future the fire brigade will need to send two trucks to every crash in case it involves a H/EV?

I'm a bit surprised there hasn't been more public discussion about the extra risks posed by H/EVs in an accident.