This morning when I started up my engine revved to 2000rpm for 10 to 15 seconds and then settled down to 1000 and after driving 2 miles my idle was normal. Upon restarting warm there was no problem. This evening I went out and started it again and again the engine revved to 2000 rpm for 10 to 15 seconds and then dropped to about 1100rpm. What would be causing this problem?

When my air conditioner kicks in it seems a little rough. Kind of a thunk. It is a 2.3 and I can't even see the compressor. Can anyone give me some advice?

Day 2 started the same way with engine revving to 1500rpm then 2000. After 10 to 15 seconds it settled down. Drove 2 to 3 miles CEL light back on. I had had the CEL on two weeks ago and scanned codes 0170 and 0173 fuel trim malfunction. I had reset the codes and reset the fuel trim by dissconecting the negative side of the battery. I have driven about 125 miles since I reset them until today when the CEL came back on. I guess I will check the codes again and try to find a good mechanic or dealer. Checked codes again and got a code 0170.

When I called a dealer he said it could be a mass air flow sensor. By the way the car only has 37700 miles. I am hoping that my extended warranty will cover this.