I have a 91 Accord w/200K on it. Since I've had it, (@1 yr) it doesn't idle smoothe. It goes from about 600rpm to about 1500 rpm, back and forth. I've always thought it might be a sensor (but which one?????......) While playing around with it, I unplugged the throttle control sensor, which makes the "check engine light" come on. When the sensor is unplugged, it does idle better, but it idles at a constant 2000 rpm (a little too fast). I don't know a thing about how to check the codes/diagnosis it myself, and am to the point to eat it and take it to the shop. Any help would be great (PS: its a 4 cyl. 2.2L) THANKS!!!

 

Search idle and I bet you come up with like 20 threads.

It sounds like your IACV (idle air control vavle) is bad. You can either clean it or replace it. But from the idle bouncing thats what it sounds like to me.

Also check your radiator fluid, and ensure a clean air filter.