Author Topic: What's this bit...  (Read 716 times)

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martym00se72

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What's this bit...
« on: March 14, 2018, 06:19:28 PM »
Hi Folks,
time to play 'what's this bit'. STILL chasing down the cause of my hot high idle. Thought maybe AAV or air leak but after tweaking with this bit I dunno....

So on a hot engine I idle at about 1400 rpm. If I squeeze either of the large hoses it drops to 900-1000 or so - acceptable idle, goes back up when released. If I squeeze the smaller hose on the right, it makes no difference. If I take the smaller hose off at the plenum, it makes no difference (what the??) but there is vacuum on the plenum when I block it off with my finger at the plenum.

So I figure this is supposed to be some vacuum activated extra air device of some kind but why and what is it supposed to do? I figure mine is not operating correctly so how do I service it and determine correct operation? Is it needed?
thanks
Marty

PS - what is with the piddly little file size for a photo?? I keep having to resize it down to get it to fit :(
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CitroŽnbender

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Re: What's this bit...
« Reply #1 on: March 14, 2018, 06:21:31 PM »
It looks awfully like a fuel pressure reg!

martym00se72

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Re: What's this bit...
« Reply #2 on: March 14, 2018, 06:33:56 PM »
I can assure you that it is not that! The fuel pressure regulator is at the front of the fuel rail. This is mounted on the driver side of the plenum. Thanks for looking.
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LukeC

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Re: What's this bit...
« Reply #3 on: March 14, 2018, 09:29:28 PM »
Not sure how it works, but it is probably what is behind the issue. I am pretty sure it allows extra air into the engine when you back off, then closes completely. I am not sure if it is for emissions or what, but some cars it is controlled by the ECU and is over on the RH panel near the altitude compensator.

Just remove it and block all hose ends. If you still have issues, I may have one floating around.
Luke Clayton

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Duk

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Re: What's this bit...
« Reply #4 on: March 14, 2018, 09:43:30 PM »
It's an auxilary air valve.
If it's not working correctly, maybe it's gummed up with nasty manifold smeg. Taking it off and cleaning the internals with carby cleaner may be the answer to getting it to work properly again. If that doesn't fix the problem, get another one.
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LukeC

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Re: What's this bit...
« Reply #5 on: March 15, 2018, 07:23:19 AM »
The cold start auxiliary air valve is mounted on the rear lower RH tappet cover and has an electrical connection to it. This is operated by high vacuum. Alfettas used to have a switch operated solenoid mounted on the carbs for the same purpose.

Answer is on this web site:

http://www.alfaclubvic.org.au/forum/index.php?topic=4473.0
« Last Edit: March 15, 2018, 07:26:06 AM by LukeC »
Luke Clayton

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martym00se72

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Re: What's this bit...
« Reply #6 on: March 15, 2018, 09:23:23 AM »
Brilliant, thanks folks. Truly useful information from the collective yet again.
'83 GTV6 - 3.0 is in! Ohhh yeah!

What do people do with their old 2.5...?

sportiva

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Re: What's this bit...
« Reply #7 on: March 15, 2018, 08:47:43 PM »
It is a deceleration valve that allows air into the plenum on a closed throttle allowing any excess fuel to burn off.
It's a pollution control device that works off a vacuum in the plenum. removing it will make no noticeable difference to performance but you might need to  reset the idle speed so check all your hose for air leaks. I removed mine when the 3 litre went in two years ago with no issues.
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martym00se72

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Re: What's this bit...
« Reply #8 on: March 15, 2018, 10:11:43 PM »
What's the best way to block the holes to make sure nothing gets sucked into the engine?
'83 GTV6 - 3.0 is in! Ohhh yeah!

What do people do with their old 2.5...?

sportiva

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Re: What's this bit...
« Reply #9 on: March 15, 2018, 10:31:52 PM »
Bolts with thread tape or cut the head off a bolt and cut a groove for a screwdriver even with the head missing the shoulder of the bolt wont allow it to screw it's way into the plenum and it looks neater
3.0 GTV6 156JTS X2

75 2.5
2.0 Alfetta Sportiva #22
1.8 Alfetta
1.2 alfasud
2 75 parted out
15 alfettas parted
10 gtv parted
5 alfasuds parted

Car forums usually have more philosophers than practitioners