Okay, my car has been doing this thing where the rpm's will go down to about 500 for a second when it's idling sometimes, and then it will come back up to normal. Well today, I cut the car on, and the little bastard when down to 300 and then cut off. I am assuming that the IAC valve is causing this- it's not working right or something. I'm wondering though, if the IAC valve might not be closing when it should and giving the engine too much air, making it run lean and making the car detonate. I know that the O2 sensor isn't getting a lean signal. Is it possible that the MAP sensor is reading that the car is too lean, but maybe it can't compensate enough? I know the computer is getting some kind of signal that is making it run like this, cause I unhooked the battery and rehooked it and the car ran wonderfully for about 20 miles or so, then started this same detonation **** it's been doing. Any ideas??

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With this car, it's never a question of "can I...", only "will I..."!

 

LBC,

Try removing and cleaning/lubricating the IAC. It might be getting sluggish.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Is there a way to check and see if the IAC isn't working right? I'll be cleaning and lubricating it this weekend, so we'll see if that has any effect.

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With this car, it's never a question of "can I...", only "will I..."!

 

What do you use to lubricate the IAC?

Thanks,

Ken

[This message has been edited by Ken88GTA (edited July 03, 2001).]

 

Just buy a new IAC, mine went bad after 50,000 miles, it fell apart in my hands when I try to set it. Thats how bad it was. You won't set a code if the IAC is bad, thats the funny thing, but if the MAP sensor is bad it will set a code.

 

Ground the A & B terminals of the ALDL port and go up to the IAC and put your ear close to it. You should hear a ticking type sound coming from it. This noise is the ECM opening the IAC. Also, you can test it by running the car with the IAC unplugged. The idle with the IAC unplugged should be about 100-200 RPM lower than it is when the IAC connector is plugged in.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson
#3
'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Edelbrock Intake, Accel Runners, Comp Cam, Crane Gold rockers, Lucas 24# injectors, Edelbrock headers, Flowmaster 3'' exhaust, Mallory Ignition, Transgo Performance Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

 

I tested it via kens instructions and when I bridged the A&B terminals it would run and then constantly run until you cut the key off. Then when I ran it with it unplugged(terninals not bridged) it idled, if you can call it that, at 2250RPM. What does this mean, The IAC didnt sound very healthy

 

As far as I know, when you shut off the car, your IAC will open all the way. This way when you start the car the next time, it will go to a high idle. So if you unplug it, it will stay at a very high idle because it cannot close.

 

By the way, my car is doing the same exact thing when it is cold. It takes a second for it to jump to a high idle and almost stalls. I think I'm going to clean the hell out of my Throttle body this weekend or just replace the IAC but I am concerned that the ECM is not giving my IAC the correct signal at startup.

 

I had problems with mine too and I used some GM stuff called "Cleens". It is a combustion chamber cleaner and you can get it in spray or pour bottle. It takes away all the carbon. I just spray it in the hole when it is running and it cleans everything out nicely. If I were you I would invest in a new IAC and save yourself a lot of headaches because it is going to be more PITA down the road and you will be extra frusterated then!