When the a4 1.8t is cold runs fine. When it gets warm it starts acting funny, the rpm guage flictuates every few seconds like it gets power real quick. Its every 3 seconds. Its got paddle shifters. Anybody know the dealio? Tranny flish? It has 110,000 miles. I got a po420 code said catalyst below threshold bankone. I deleted it and its not back on. Anybody?

 

Does the speed of the car changes or just the RPM?

 

My '99 2.8 does the same thing, but only when I'm in neutral. I haven't figured out why yet, though. I thought it was because my valve cover gasket was leaking oil onto my spark plugs, but after I replaced the VCG, the plugs, and wires the problem persisted.

 

Well im not sure really, seems like just the rpm when it gets operating temp, its fine cold? Mine dont do it in neutral.

 

Something tells me that your mass airflow sensor is bad. Try unplugging it and see how it runs. If no change its bad. Do you get a orange triangle with a circle around it? Or any check engine code?