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I've been having a problem with a lumpy idle for a while now and last weekend after doing lots of reading here on the forum I finally did some work to the car. I replaced the oxygen sensor that was randomly throwing some error codes near the end of last year and has been in my tool box to replace since December. I took off the throttle body, removed the idle air control valve and cleaned both of them thoroughly. I reattached it and upgraded the intake to a K&N 57 Series Gen II short ram kit. I did the ECU re-learn and all seemed well.

But during the week I noticed when stopped at lights that sometimes the lumpy idle would return. I'll try and describe it as best i can. The rpm's don't fluctuate and stay at 800rpm. When it happens I can feel it coming though the car, as if it was bouncing a little or something. If I press the accelerator even the smallest amount it stops, but when it goes back to 800rpm it usually returns, sometimes it doesn't. Timing belt and spark plugs were changed in December and oil was changed 2 weeks ago when the garage fixed the leaking oil pan seal.

Any suggestions to the cause of the problem would be greatly appreciated

 
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Anyone?

 
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i dont think anybody knows what you mean by your description or "lumpy idle"

it might help if you post a video

 
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I don't think a video would do any good, you can't hear any difference in the sound of the engine, you actually feel it coming through the car when you are sitting in the car, as if the car was travelling over very consistent, small smooth humps on the road. It's not the easiest thing to describe