Ok i have a 91 Eclipse GST 2.0 and it idles very wierd it wont idle at a steady pace, and it always goes from about 1300-1500 just up and down, up and down, it bugs me so i want it fixed and no it is not the O2 sensor because i just replaced that a couple days ago, i was thinking maybe ECU, but im not sure....help?

 

Im lost on that one... but maybe this bump will get someone who knows to look

 

throttle position sensor......? thats my best guess............. is the radiator fan switching on and off? i know when the fan comes on and goes off... that causes a small idle shift in my car, its not a lot, but you do notice it....

 

I have a 93 same car and just had it fixed and it was the idle air control valve. doing exact same thing............

 

Did you have to replace the idle air control valve or just clean it? If you had to replace it how much did it run you?