I ran a search but couldn't find the info I was looking for. Can anyone help me deduce this problem?
My car had a rough idle; cylinders misfiring, engine shaking, the works. It also affected the car when in gear at low RPMs; it would hesitate, not responding to the accelerator until it was past halfway then surging to the power it should be providing at that level of throttle. It would not do this when revving out of gear.
Anyway, I was directed to several areas. Spark plugs and wires are both less than a year and ten thousand miles old. I checked them and everything was tight. I have also been told the forward Oxygen sensor may be at fault, but further investigation has led me away from that.
I was also directed to the Idle air controller. I pulled it off and cleaned it with a rag (it was black and filthy), and also cleaned out the hole into which the sensor goes. It had no effect for about half an hour of driving, but after a while there was no hesitation when starting in gear, and the engine idled better, though not as smooth as it used to.
This weekend the problem returned. Same rough misfiring idle, same hesitation starting in gear. To test the success of cleaning the controller, I cleaned it again (it had almost nothing on it), and the same thing happened, a half hour later it was almost back to normal.
What I want to know is, is this a sign the idle air controller is the culpret, or is there something else that I'm affecting when I clean it? I'm trying to get hold of an idle air controller to test locally, but I also wanted to see if anyone may have a diagnosis I haven't considered.