idling problem when slowing down
Thread Starter
Instructor
Joined: Oct 2011
Posts: 138
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idling problem when slowing down
My 2002 C5 has this problem where when you are slowing down, the idle will be high (between 1500 and 2000rpms, sometimes higher). When you come to a complete stop, like zero MPH, it will go back to normal idle. It doesnt do this all of the time, but more times than not. Kind of annoying considering the car is loud. Usually worse when AC is on.
My first guess is the idle air control valve. I found one real cheap online but dont want to buy and install it if its not the problem. I already fell victim to the ignition bypass box thing and that was a nice waste of an afternoon.
So am I guessing right, or is there some other gremlin at work here?
Thank you. I tried searching but couldnt find this exact problem on here.
P.S. my other guess is maybe it just needs a tune. It has not been tuned since the Vararam was installed and is throwing a CEL for lean condition. It has MS3 cam, LG headers, hi flow cats, etc if that helps.
My first guess is the idle air control valve. I found one real cheap online but dont want to buy and install it if its not the problem. I already fell victim to the ignition bypass box thing and that was a nice waste of an afternoon.
So am I guessing right, or is there some other gremlin at work here?
Thank you. I tried searching but couldnt find this exact problem on here.
P.S. my other guess is maybe it just needs a tune. It has not been tuned since the Vararam was installed and is throwing a CEL for lean condition. It has MS3 cam, LG headers, hi flow cats, etc if that helps.
Race Director
Joined: Jan 2006
Posts: 10,554
Likes: 33
From: Not on either liberal coast.
You might look into this HALLTECH product...
http://www.halltechsystems.com/Hallt...r_p/hc.125.htm
Just for the heck of it, you might do the GM "idle relearn procedure"...
http://forums.corvetteforum.com/c5-t...procedure.html
http://www.halltechsystems.com/Hallt...r_p/hc.125.htm
Just for the heck of it, you might do the GM "idle relearn procedure"...
http://forums.corvetteforum.com/c5-t...procedure.html
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Your LS Engine doesn't have an IDLE CONTROL VALVE.....
With all those mods,,,, has it ever been tuned??? I hope so!
The addition of the VARARAM shouldn't change enough to cause a cell if all the other things are working correctly. Clear the DTCs and see what come back
Your IDLE issue sounds like a vacuum leak!! Check the entire PCV system as that has a tendency to ROT and cause a vacuum leak.
Check the intake air ducting between the MAF and the Throttle body and make sure that it is not leaking.
You also should clean your MAF with MAF cleaner. Spray it on and let it dry. While the air ducting is apart, also clean the Throttle Blade/Throttle Body.
Your engine idle is controlled by the position of the throttle blade. The PCM sets the idle speed and open or shuts the Throttle Blade to control it.
Just for grins,, does your Throttle Blade have a HOLE drilled in it??????
If turning the AC on effects the Idle speed /Idle Quality,, that could be the result of a poorly tuned PCM. Some People drill holes in the Throttle Blade to fix an idle issue,, If they did, they are NOT doing you any favors..
BC
With all those mods,,,, has it ever been tuned??? I hope so!
The addition of the VARARAM shouldn't change enough to cause a cell if all the other things are working correctly. Clear the DTCs and see what come back
Your IDLE issue sounds like a vacuum leak!! Check the entire PCV system as that has a tendency to ROT and cause a vacuum leak.
Check the intake air ducting between the MAF and the Throttle body and make sure that it is not leaking.
You also should clean your MAF with MAF cleaner. Spray it on and let it dry. While the air ducting is apart, also clean the Throttle Blade/Throttle Body.
Your engine idle is controlled by the position of the throttle blade. The PCM sets the idle speed and open or shuts the Throttle Blade to control it.
Just for grins,, does your Throttle Blade have a HOLE drilled in it??????
If turning the AC on effects the Idle speed /Idle Quality,, that could be the result of a poorly tuned PCM. Some People drill holes in the Throttle Blade to fix an idle issue,, If they did, they are NOT doing you any favors..
BC
Tech Contributor
Joined: Sep 2005
Posts: 1,731
Likes: 82
From: New Market AL
It sounds like you have already had somebody tune this? More than likely they left you with too much airflow in the RAF idle table. That will cause the idle to hang until you come to a complete stop. Another tuning problem I ran into is when the ignition timing idle tables have large differences with the high octane table. Smoothing tables is your friend. Find a competent tuner.
