I know this topic has been beat to death, but I have a few questions on the idle of the car that I can't seem to find any info on.

firstly, when i got the car, it wasn't running great....was very rough idling, suring, etc. Drove the car for a bit and it worked itself out. However, car still would not drop rpm's readily...would always take a little time.

Last couple of days the car has been missing when driving at a constant speed (between 2000 - 3000rpm). I haven't pulled the IAC off yet, as the weather has been crappy. What I have done is cleaned the intake a couple times with GM Cleens (aka Sea Foam). The first time, it made the car run horrible...drove it a little hard and it began running better. However, it still had the miss while driving.
The last time I cleaned it (last night), it seemed to make it worse originally. Took the car out for a run and the rpms would hang at 2k until the car was completely stopped (then drop to 900 or so). After driving for maybe half an hour, the rpm's now drop to around 1200 until the car comes to a complete stop, they then drop to about 950. Thankfully, the car no longer has the miss while driving.

I guess, after this long winded explanation, what I want to know is, how should the RPM's act when you push in the clutch while driving at any speed? should they instantly drop to 900 or should they hang a little until the car slows down?

thanks for any information...sorry about the long read


Nick

check vacuum leaks around hte intake and check your hoses for leaks. Take some carb cleaner and spray it around everywhere one piece mates to another. if the idle rises you have a leak there. I had the same prob with my car, was the intake manifold gasket. Better to find the source then to replace everythign that isnt bad.

my idle tends to hang just over 1k and then down to like 700-800 when im completely stopped.

if your car is missing then you might wanna change the spark plugs. Use the cheapest NGK V-power plugs don't use any platinum 4 or split fire bullshit.

I have changed plugs and check wires for any breaks....wires checked out okay.

As for the car missing...its more than a miss. If driving constant at 2500rpm in 4th gear, when it happens, the rpm's drop to about 2k for a split second and then rise back up again. Also very easy to feel the drop in power for that split second. I am fairly certain that it was caused by the IAC as it is better now after cleaning with intake cleaner.
However, I am still unsure if the way the rpm's are acting is correct.

I defintely will check for leaks around all gaskets when the weather clears up a bit.

Thanks a million for the help


Nick

Shouldn't the IAC be completely closed at WOT or cruising? So I don't see how it would effect anything while cruising. It should be closed and if even if it opened it'd only raise the RPMs wouldnt it, by allowing more air?

And yeah, my car does the same thing. It'll hang above 1100 til I completely stop. Maybe a safety mechanism to keep vacuum in the brake master cylinder so you can break more easily? Or maybe power steering even.

Joseph