Stalling
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Joined: Dec 2021
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From: Atlanta GA
Stalling
I was wondering if anyone had any insight into this problem.
1985 C4 runs fine but when warm it will eventually wind down from an idle of about 700 to 600 to 500 etc and die. My IAC is new. Adjusting the idle screw doesn't make a difference. What I have to do is shift into neutral at a light and the RPM comes back up by itself. If the car does die, it start right up no problem.
My distributor and components are also new.
I was wondering if it was fuel pressure. I seem to remember reading or watching something that ascribed this type of problem to low fuel pressure. I have an adjustable FPR. I was going to adjust the screw on the FPR in. That should increase fuel pressure.
Does this seem reasonable?
My other concern was my MAF.
Do you have any thoughts that would help me.
Charles
1985 C4 runs fine but when warm it will eventually wind down from an idle of about 700 to 600 to 500 etc and die. My IAC is new. Adjusting the idle screw doesn't make a difference. What I have to do is shift into neutral at a light and the RPM comes back up by itself. If the car does die, it start right up no problem.
My distributor and components are also new.
I was wondering if it was fuel pressure. I seem to remember reading or watching something that ascribed this type of problem to low fuel pressure. I have an adjustable FPR. I was going to adjust the screw on the FPR in. That should increase fuel pressure.
Does this seem reasonable?
My other concern was my MAF.
Do you have any thoughts that would help me.
Charles
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
When you say that your IAC is new did you replace it to try and fix this issue? Or did the problem start after replacing it? It's getting more and more common that IAC's are junk out of the box. I just went through this issue with mine.
Also check the connector for the IAC. Make sure it's free of corrosion and in good condition. If it's at all suspect I would solder on a new plug.
Also clean the throttle body. Carbon build up in the IAC opening can cause all kinds of problems like this. Even with a new IAC that is working properly.
As far as fuel pressure goes I wouldn't think low fuel pressure would cause it to stall in gear like what you're describing. But that's easy enough to find out. Put a fuel pressure gauge on the rail and see what your fuel pressure is. If it is too low then bump it up.
Are there any codes?
Also check the connector for the IAC. Make sure it's free of corrosion and in good condition. If it's at all suspect I would solder on a new plug.
Also clean the throttle body. Carbon build up in the IAC opening can cause all kinds of problems like this. Even with a new IAC that is working properly.
As far as fuel pressure goes I wouldn't think low fuel pressure would cause it to stall in gear like what you're describing. But that's easy enough to find out. Put a fuel pressure gauge on the rail and see what your fuel pressure is. If it is too low then bump it up.
Are there any codes?
Pro
Joined: Jun 2018
Posts: 658
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From: Louisville, Ky
2022 C4 of the Year Finalist - Unmodified
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There is a certain procedure that must be followed to adjust the IAC and the TPS on early C4's.
https://www.corvetteforum.com/articl...ps-idle-speed/
HTH,
Joe K
https://www.corvetteforum.com/articl...ps-idle-speed/
HTH,
Joe K
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Joined: Dec 2021
Posts: 97
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From: Atlanta GA
Thanks everyone for your responses.
The IAC was placed a while ago by me before this was an issue that was occurring.
I will take apart and clean the throttle body, MAF assembly etc.
I do not have an OBD 1 reader unfortunately.
The car also has a long crank before it starts up. I did not mention that before but perhaps this has a meaning also.
Last resort could replace with a new IAC also.
Any comments on the MAF?
C
The IAC was placed a while ago by me before this was an issue that was occurring.
I will take apart and clean the throttle body, MAF assembly etc.
I do not have an OBD 1 reader unfortunately.
The car also has a long crank before it starts up. I did not mention that before but perhaps this has a meaning also.
Last resort could replace with a new IAC also.
Any comments on the MAF?
C
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Is the check engine light on? I doubt it's the MAF. This really sounds like an IAC issue to me. Some carbon buildup in the throttle body blocking the IAC opening or a bad IAC. But it can't hurt to get some MAF cleaner and clean it while your at it.
