2003 AMB engine, CVT trans. 156k miles. Startup and warmup were fine. Smooth idle and acceleration. After reaching operating temp. any moderate throttle would produce intermittent missing/bucking. This was especially bad on inclines. It would happen at any speed from zero on up. As soon as you pushed the engine up to 2-2.5k rpm it would intermittently buck.

No codes stored except the G2 coolant sensor (the gauge side of the dual sensor) intermittent short to plus. Replaced with no effect on the problem but the gauge stopped wandering. Swapped coil packs one by one with known good spare that I keep in the trunk but no improvement. I was suspicious of plugs but there were no misfire codes. Finally did get a set of NGKs $58! (Yeouch!) and the problem is SOLVED! On another thread, a poster claims that the Audi computer does not register a misfire until there are 4 in a row. That may explain why there were no codes stored.

It turns out that I had a set of Champions in there that had 2 problems. First, they were Champions (!). Second, they were getting pretty worn. Gaps were about .010 too wide with light erosion all around the ground electrode. Normal grey color. I cannot complain as the wound was totally self inflicted. I tried to get the right NGKs last time but was unable and leveraged for time. I bought the Champions with the intent of replacing them but never got around to it and eventually forgot about it.

I could not find any thread in this forum or anywhere on the 'Net pointing to bad plugs causing bucking so I decided to post this.

Good Luck out there.

 

Nice writing! Thank you!