If my cars been sitting and its completely cooled down and I start it up it will be idling around 1500. Once it warms up and I'm stopped it will idle around 1000 but fluctuate back and forth between about 750 and 1000. Once it's warmed up it seems to idle alright, although I have noticed a few times where it is still idling around 1500 even after its been running for a while.

Also I noticed when I press my brakes hard when I'm stopped, it will jump up from idling around 1000 and go up close to 1500. Not sure if they all do that or not, just something I noticed when I was messing around trying to see figure it out.

 

bumpskis

 

Sounds like it could be o2 sensor?

 

If It's the o2 sensor then I'm glad, as I have plans of replacing that anyway since reading the thread about MPG and o2 sensors.

Anything else it could be?