Hey guys, hopefully you can help me out with this. I'm trying to figure out what is causing the car to idle at an unusually high rpm. When the car is in motion and I engage the clutch it will idle at 2,000 - 2,500rpm until I come to a stop, then it will drop to about 1,100rpm. I was thinking that it might be the idle air control, but I don't know how to be sure aside from buying a new one and trying it out.

Any thoughts?

 

Try removing the one you have now and cleaning it. My 89 had that problem i replaced it and I could have just cleaned the old one. Also could try the bp sensor.

 

Thanks for the info! I'll try cleaning it later this week and post the results.

 

check/clean the MAS, and TPS throttle position sensor.

It appareantly is a pretty common issue with the 3.8. The culprit is usualy a dirty sensor of some sort. Cleaning the two above lowered mine back down to about 1,000rpm.

I can see if I can't find what other senors could cause it if this doesn't work.

 

The IAC is also one that has caused it on others.

 

One more thing it could be is the throttle body blades but i would try cleaning everything fore mentioned first. Those got dirty on my 05 and it was freaking out

 

Check for a vacuum leak too. The computer tries to compensate for low vacuum with higher RPMs to hopefully produce more vacuum. My car did the same when very few of my vacuum lines were still intact, so that's worth taking the time to look at.

 

Ok, I took everything apart... Removed CAI, cleaned the MAS, throttle body, IAC, and TPS. That didn't seem to do the trick, but I now have a check engine light staring me down. I decided to run the car with the TPS unplugged and everything seems fine, aside from the check engine light. Guess I need a new TPS?

The only thing that I haven't done yet is check for vacuum leaks. I'm not sure how to go about going that.

 

Check the voltage on the tps it shoult be between .7 and 1 volt with the throttle closed

 

When I see check engine lights at a time like that I thank the Lord. If you have an OBDII reader this is the time to use it. If not, I just picked one up at my local auto parts store for 45 bucks. It's a great tool to have when dealing with electrical gremlins.

Read the code and let us know what it says. As for the vacuum lines I would just suggest poking and prodding at them. On my car it was pretty obvious that most the lines looked like they had been half eaten by rats, but you should be able to hear most any vacuum leak if you get your ear close to the line.

 

I hooked it up to the voltmeter and got a reading of .987 volts at idle. If I slowly rev up the engine it'll go up to about 2 volts. If I do it quickly the voltmeter reads OL (Overload).

Yea, at least the computer now agrees that there's a problem. I'll have to go pick one up... I've been meaning to get one for a while now anyway.

All of the lines seem to check out fine. I couldn't hear or see anything that looked problematic.