Idle problems on c4s
Thread Starter
Pro
Joined: Oct 2001
Posts: 725
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From: Berlin Maryland
Idle problems on c4s
I have tryed every thing to fix my c4s idle problems. Replaced mas, tbs,Idle air motor.Removed throtle body and plentem cleaned and found no worn or sticking parts.Set tbs and idel to factory specs.Still when I start it up it runs from1400 to 1700 for up to 8min then out of no where it goes to 600 and then runs perfict,until I stop it .then it starts all over again.
What should I look at next? :confused: :confused: :confused:
What should I look at next? :confused: :confused: :confused:
Pro
Joined: Mar 1999
Posts: 678
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From: Oslo, Norway
Re: Idle problems on c4s (plumberh2o)
Hi.
I have an 85. Had idle problems. Have you checked for vacuum leakages. If you have one the idle air motor wants to compensate and that can do some cycling of the rpms.
What was my problem was the EGR valve. It can either be the valve itself (the mechanical part) or it can be the Vacuum membrane that is defect. The easiest way to test the vacuum membrane is to take a vacuum pump and apply vacuum on the vacuum intake. It shall hold the vacuum for at least 30 seconds. If it doesent and holds it for about 15 seconds . Change the valve.
It can also be the toroid for the EGR system. Check that it is described in the book(easy test). It can also be the EGR temp sensor.
All in all I believe that the EGR valve is the most probable cause.
Good luck
Jan-Erik
I have an 85. Had idle problems. Have you checked for vacuum leakages. If you have one the idle air motor wants to compensate and that can do some cycling of the rpms.
What was my problem was the EGR valve. It can either be the valve itself (the mechanical part) or it can be the Vacuum membrane that is defect. The easiest way to test the vacuum membrane is to take a vacuum pump and apply vacuum on the vacuum intake. It shall hold the vacuum for at least 30 seconds. If it doesent and holds it for about 15 seconds . Change the valve.
It can also be the toroid for the EGR system. Check that it is described in the book(easy test). It can also be the EGR temp sensor.
All in all I believe that the EGR valve is the most probable cause.
Good luck
Jan-Erik
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: Idle problems on c4s (jan-erik)
My car was not acting up that much but I had a stalling problem when revving the car up and let it come back to idle it would stall. It would also surge quite a bit. Turned out it was the battery! It always started, but it was definately the battery.
You should time it and see if it is always the same amount of time. It too sounds like the EGR. Could be associated with the close loop ECM function too.
Try the EGR and battery just for starters. I have an EGR what I too out of my car if you need one. Let me know.
[Modified by ski_dwn_it, 8:27 AM 7/3/2002]
You should time it and see if it is always the same amount of time. It too sounds like the EGR. Could be associated with the close loop ECM function too.
Try the EGR and battery just for starters. I have an EGR what I too out of my car if you need one. Let me know.
[Modified by ski_dwn_it, 8:27 AM 7/3/2002]
