Sometimes if I'm stopped for a period of time whether it's in park or drive, my car will shake a little and then slightly rev a little above one on the rpms. What could that be?

 

Do you have the A/C or the defroster on when this happens?

 

Nope. I don't usually have anything else on besides maybe the stereo when it happens.

 

Could be caused by the extra load put on the alternator when the cooling fan kicks on. The IAC motor will kick the idle up some to compensate for the load.

 

So it's nothing too bad?

 

It sounds like it could be O2 sensor... Do you ever experience any hesitation when you accelerate?

 

Not at all. My car runs perfectly fine. It'll just do it maybe once or twice a week. The only thing that I know is that the cat converter needs to be replaced (which I'm doing Wednesday) and the ac is out. Not only does the car rev a little but it will jolt forward just an inch when it does it while I'm in drive. In park it doesn't jolt forward.

 

If it's jolting forward when the idle “rebounds” you should definitely check the O2 sensor. It takes all but a minute and can save you a headache trying to diagnose other components.

Once you’ve found the sensor it’s pretty obvious how you disconnect it (there is snap on connector). You will get a CEL when you do this, but that will go away after a bit once you’ve reconnected the sensor. Running without the sensor will not cause damage to your engine. You’ll notice a modest drop in MPGs, but that’s it.

 

I'll probably just have it looked at when I take it in or the cat converter. It doesn't happen to the point where it bothers me. The CEL is on periodically but I think that's because of the converter.