Idling

[Red94sc2]

I had posted a thread earlier about an idling problem I have been having. It was suggested that the cracked vacuum line I had was the problem but I have since replaced that and the problem is still there.

I have cleaned the T-Body several times including the TPS and the IAC. I also cleaned the EGR valve.

What the car is doing is that when first started, it will idle between 1000 and 1500RPM. After driving a while, when you come to a stop it will dip to 500rpm, back up to between 1000 and 1500rpm a few times then will sit and idle between 1000 and 1500rpms.

What would cause this variation in idling? Could it be the IAC? I disconnected the IAC to see what happens and it idled with no flucuation but at 3000rpms since it was not connected. I have cleaned the IAC and TPS. Could the IAC have gone bad? Someone had mentioned the ECTS. Would the ECTS cause a flucuation and high idle. I have not found any more vacuum leaks.

Thanks for any input.......

[Twin_Cam]

It's unlikely, but check for leaks on the air intake tubing, especially at the crankcase vent hose (the hose coming from the cam cover). I forget to connect this hose before, and my car displayed these symptoms. The revs would dive so bad I'd have to rev the engine to keep it running.

[wolfman]

To confirm or deny that you have a bad IAC valve, do this:

Start the car and allow it to warm up to normal operating temp.

Turn off the car and disconnect the IAC electrical connector

Plug the IAC passage in the lower throttle body throat with the IAC valve STILL INSTALLED (A piece of duct tape will do, or your finger pressed firmly to seal the pencil sized hole)

Restart the car.

IF with the IAC disconnected and port plugged the car idles around 600 RPM or so warmed up, the IAC is bad. If it is substancially higher than that, and YOU HAVE NOT messed with the throttle stop screw, you have a vacuum leak that the IAC has been trying to compensate for resulting in the odd idle behavior.

[Red94sc2]

Thanks for the tip. Ill try that today after work..... Thanks again....

[Red94sc2]

Got the problem fixed! It was not the IAC but it was the ECTS!!! I had my valve cover gasket replaced in my parking lot at work by a mechanic at my local Saturn dealership that works on the side. He looked at the idle and said, like most of you have said, that the ECTS may be bad. I replaced it with one from AutoZone. The old one was cracked on the tip! As soon as I started, it idled like brand new and havent had a problem since!!!! Ill be replacing the one on my 95 SL2 soon just in case.......