So I've been trying to figure this out for a couple weeks now. I have had no luck. I am hoping somebody here has had a similar experience that can point me in the right direction.
Well basically this all happens when coasting in nutural with my foot off the clutch. Once you come to a complete stop in nutural, the RPM gauge will idle properly. When coasting however, it's almost like an idle flare where the idle will raise on it's own as if I am pushing the gas, then other times the RPM gauge will drop to .400 then jump right back up to the proper idle. Take in mind this is ALL the time. It's 70-80% of the time.
So here is what I have already done. Pulled the throttle body off and cleaned with throttle body cleaner. Inspected for any hose leaks (could have missed).
Well I hope somebody here can help me.
I love the forum!!
Mike
I was doing a little more research and came across an article related to an idle problem for a 2002 cavalier. It is said to change the MAF sensor. The reason the computer is not picking it up is because the circutry in the MAF sensor gets corroded with air something and it's not enough to trigger the computer to throw a code.
Anyones thoughts is very much appreciated.
Mike
Mike Johnson wrote:I was doing a little more research and came across an article related to an idle problem for a 2002 cavalier. It is said to change the MAP sensor. The reason the computer is not picking it up is because the circutry in the MAP sensor gets corroded with air something and it's not enough to trigger the computer to throw a code.
Anyones thoughts is very much appreciated.
Mike
Fixed for you, J-bodies use a manifold absolute pressure sensore, not a mass air flow sensor to guage the amount of air being utilized by the engine at any given time. Make sure you checked the hose connection to the MAP sensor, as well as the wiring plug, also might be a good idea to remove the IAC from the throttle body and give it a thorough cleaning as well as the bore it mounts to.
My manual trans equipped car coasts with the idle higher than it is when at a full stop, something like 1500 rpm, as I slow down further it idles down to what it is supposed to be. I dunno if it would give you any ideas, but at a stop I can pump the brakes and the idle will flare up, and sometimes when it drops back down it goes down to around 400 rpm, but I believe thats the IAC trying to keep up with me bleeding off vacuum by pumping the brakes. It DOES sound like you may have a vacuum leak somewhere.
I hate to ask you this, do you have some pictures showing where the MAP sensor and the IAC are on the engine?
I am 99.9% sure I found the IAC valve. I pulled it out and there was a spring at the end with sort of a cap over it. At the other end closer to the plug there was a gold looking coil. I took throttle body cleaner and only sprayed it in where the spring was. I also sprayed the bore where the valve connects to the TB.
After completing this, it made no difference with the idle issue. I search about a PCV valve and realize there is no PCV valve on these motors. So now I'm looking to find where the MAP sensor is. Can you point me in the right direction?
No, sorry, no pics at all of the Eco MAP location, best thing I could suggest is tracing the vacuum lines from the TB, the largest should go to the brake booster, a small one to your tranny (if auto), the MAP sensor one should be about 1/4" diameter I THINK. And come to think of it, I don't know where the MAP sensor is on MY engine (2200), need to look for it one of these days I guess.
That little "cap" over the spring if it was pointy like a cone, that was definitley the IAC, that little cap is the pintle that meters the air, the IAC motor draws that in and out of the bore to control the idle.
Edited 1 time(s). Last edited Sunday, August 12, 2007 7:21 PM
I never pulled that cap off. I just sprayed right in between there with TB cleaner.
I will start tracing for the MAP as soon as I can.
Thanks again!
