Hello,

I'm trying to troubleshoot a stupid weird idle problem. I turned car off, and unplugged the IAC connector to reset.. I backed off the throttle blades _ALL_THE_WAY, but the idle was at like 1200 RPM. Your suposed to set it to like 450RPM in N according to my service manual, yet it revs like a ****.

With IAC connected, it idles at 650 RPM, fairly well - sometimes. Sometimes it starts chasing between about 400 and 900 RPM, and occaisionally just quits.

O2 readings appear to be around .400-600 at idle, fuel pressure is at 45PSI today. Playing with that does not help.

I sprayed _EVERYTHING_ (hoses, intake, EVERYTHING) with carb cleaner, absolutely no apparent vacume leaks. Inspected the rails and injector seals, no leak. The rails don't leak down after I turn off either.. Maintains like 40psi..

THis sometimes causes a hard start, sometimes doesn't.. I'm leaning twords the IAC motor being junk. I've read a few posts of people not running IAC, and just using throttle blade adjustment, or PE vs RPM tables in the prom. But mine idles like mad without the IAC, perhaps because of the blower?

Sorry that this is long, but this is truely got me troubled. Usually this stuff ends up being simple stupid things.

Thanks!

-- Joe

 

Try this method. Turn the key on but don't start the car. Jump pins A&B of the ALDL connector and let it sit for 30+ seconds. With the key still on and the ALDL still jumpered, remove the connector from the IAC. Next, remove the jumper from the ALDL and start the car. Now, set the Idle to around 500 in neutral and then shut offt he car. Reconncet the IAC and start the car , check your idle quality now. If it still hunts for idle after this then replace the IAC, if you are sure there are no vacuum leaks.

 

like he said !! turning the ignition to the on position for 30 seconds allows the IAC to reset itself

 

I agree with Morely. About the only thing you may wish to consider is the "base idle speed". If you have a larger cam and running a higher idle speed in the eprom, it is sometimes a better idea to run a higher "base idle speed" when your reset the IAC.

The 450-500 rpm "base idle speed" is for a stock engine where you will only idle around 600 rpm in drive (if an auto). This "base idle speed" becomes your "limp idle speed" should you ever go into limp mode.

That is why on cars running larger cams that need a higher idle speed like 800 rpm to idle half decent, I will set the "base idle speed" higher to around 600-700. Also, you should increase the "fail save" idle speed inside the eprom (this is for when you have an SES code but not limp mode - the ECM still has some control).

These are things guys forget about on a modified engine - until they throw an SES code or go into Limp Mode, and find they don't have "limp mode" anymore.

 

How does one know if they are in "limp mode" Glen??

Thanks!

-- Joe