high idle even after cleaning air filter

[dyc1077]

I need to get this high idle diagnosed. I came across a bunch of threads with links to previous threads but many of the links dont work anymore. Saw some threads regarding high idle but mine is a 1999 so shouldnt be the intake manifold gasket. My air filters were recently serviced and cleaned. the TPS was replaced in 2010.

Seems like the high idle happens more so when the AC is running. The car idles around 1500 rpm. When the AC is completely off, sometimes it will drop down and idle around 650 rpm and stay for a bit but then I get hot and have to turn the air back on and the idle will jump back up. It is causing weird driving characteristics when just doing regular city driving. The car will seem to have cruise control when cruising along at 1500 rpm since the car is "idling" at 1500 rpm! A tech has suggested the AIS motor as the culprit. Is this part hard to replace? hard to find? My service manuals are on order but would like to know if this is a difficult task that I should be bringing the car in to a shop to get done or if I attempt in my garage at home.

 

[eucharistos]

most common cause is a bad ground somewhere (i've read of various grounds being the cause and i can't find the threads either with the updated website), someone will chime in soon and help both of us out. i've lived with my high idle for awhile and often use it as cruise control. mine "seems" ambient temperature sensitive, not a/c sensitive though

 

[cfiiman]

I chased an idle "hang" for a while and the I cleaned the iac etc. but the one thing that I did where I noticed the biggest difference is I ran 2 bottles of Techron through the gas. After I did that almost instantly while it still hangs for a few seconds it will drop down to where it should be. Before the techron mine would drop down eventually but then would "surge" up to 1200 or so then back down then up and so on and so forth but now it will stay down. I bought my car with around 7K miles on it and it is a 94 so I'm thinking things may have just been a little gummed up on the injectors causing it. Anyway thought I'd offer it up as a very cheap suggestion to try first. I'm still planning on replacing the iac valve just to see if that does anything as I have already cleaned it and it didn't seem to make any difference and I have heard sometimes you just need to replace them. Let me know if you decide to run a bottle if that does anything, good luck and keep us posted on any progress.

 

[dyc1077]

I decided to try a few more things out today on my drive to work. If I dont turn on the A/C, the idle stayed at below 670. Once I turned on the A/C it moved up to idle at 1500 rpm and did not drop back down even after turning off the A/C. any other things that could be causing the spike in idle caused from turning on the AC?

 

[GTS Dean]

Quite likely to be an IdleAirControl pintle that is gummy. Best to remove it and clean the heck out of it with spray. The dealer's DRB-III has a routine that can step the IAC motor up and down in 2-300 rpm increments to test for problems.

 

[Dom426h]

+1 on cleaning the IAC valve.

Fuel injectors are likely Not the problem but it cant hurt to run through some fuelinjectcleaner everyoncinawhile regardless.

 

[Jack B]

I decided to try a few more things out today on my drive to work. If I dont turn on the A/C, the idle stayed at below 670. Once I turned on the A/C it moved up to idle at 1500 rpm and did not drop back down even after turning off the A/C. any other things that could be causing the spike in idle caused from turning on the AC?

Someone mentioned the bad ground. When you turn on the AC, the fan goes to high speed, therefore, pulling a large magnitude of current. If you already have a bad ground, this could exacerbate the already bad connection. You can try bonding the passenger side O2 sensor ground wire to a bolt on the block. I Took mine to one of the bolts on the AIC because of the high idle. I later found I had a broken O2 sensor ground wire, that wire originates at or near the a/c compressor on the drivers side.

 

[dyc1077]

so i brought the car to to dealer to get the idle air motor changed out and they changed out the throttle position sensor as well.

now the car doesnt idle as high as much but it hesitates in the 1500-2500 rpm range or so when the car hasnt been driven for a few hours. the hesitation seems to go away after 20 minutes of driving but comes back once the car has sat cold for 3 or 4 hours. any ideas? i am going to be changing out the plugs soon. the dealer couldnt figure it out. the electronics checked out ok. but they noticed low vacuum. anyone run into something like this?