Errattic idling

[joshm]

Alright so there are already a few threads on this, but i just want to get a bit of help here for my specific situation. I bought the car with this issue.

Car will start, idle at about 2000 rpm, then drop to 1500, and about 20 seconds later drop to 1000 rpm or so. After i drive the car for a bit the idle will stay around 400-500 rpm and the engine will stall. Sometimes the engine will keep its idle good at around 1000 rpm or so and be fine, others it will be super low (~400 rpm), and just yesterday i drove the car cold to repark it and the idle was stuck at 3000 RPM. I turned the car off, let it sit overnight, and now it idles like usual..

Question being, do you think its the Throttle positioning sensor ? It seems like... thanks

[PhilSine]

Idle air control valve (IACV).

It's located on the passenger side of the throttle body. Remove it, clean the hell out of it with carb cleaner, and put it back on. Be sure to mark the location of the solenoid somehow prior to removing it because you'll want to be able to put it back exactly the same way it came off. If you're a little off on the solenoid when re-installing it's not a huge deal since you can rotate it back and forth a little until your car idles at the desired RPM's (around 800). You need to remove that solenoid when cleaning the IACV so you can manually rotate the valve when you're cleaning it.

You can get away with not removing the valve by simply removing the big vacuum hose that connects to the valve and shooting the carb cleaner spray down that tube while manually moving the valve with the solenoid off but it doesn't always work.

[Legacy777]

You may also have a lazy coolant temp sensor.

[kamr0n]

Idle air control valve (IACV).

It's located on the passenger side of the throttle body. Remove it, clean the hell out of it with carb cleaner, and put it back on. Be sure to mark the location of the solenoid somehow prior to removing it because you'll want to be able to put it back exactly the same way it came off. If you're a little off on the solenoid when re-installing it's not a huge deal since you can rotate it back and forth a little until your car idles at the desired RPM's (around 800). You need to remove that solenoid when cleaning the IACV so you can manually rotate the valve when you're cleaning it.

You can get away with not removing the valve by simply removing the big vacuum hose that connects to the valve and shooting the carb cleaner spray down that tube while manually moving the valve with the solenoid off but it doesn't always work.

x2 i would lean towards electric parts cleaner if you have it.

[jp233]

I had an erratic idle on my 93 wagon, so I took that IACV off and cleaned it. It was disgusting (car has about 190k on it). I used brake cleaner, which is what I clean nearly everything with that isn't sensitive to it. You can only get in there a good bit with a toothbrush, so I had to just keep spraying while black gunk kept coming out.

Idles better now, except with the AC going crazy.