Hello. A6 2.8. W/ 200k. Recently, the engine or rpms has a slight erratic rev while driving between 30-40 mph or at cruising around 70. The rpm needle moves north about 100 rpms. Meaning if I am cruising at 2300 rpm the engine will rev to 2400 then back, etc....I am not pushing then letting up on accelerator but it sounds that way.
- replaced spark plugs, wires, gas filter, crankcase hose, Pcv,air filter and cleaned air mass sensor

Note.
- Tranny shifts perfectly and fluid changed every 60k.
- 8 weeks ago I got two misfire codes on cly 1 & 2. Code has never returned.

My initial thoughts on what could be causing this flux is fuel injectors or ignition coil?

Would appreciate any thoughts on what could be causing this.

 

I have the same problem with my A4, and I was told that it may be a bad O2 sensor in the exhaust. I haven't actually gotten it fixed yet, as it only acts up some times and only when idling, so I'm not 100% sure