So I purchased my 2004 S4 MT last year and it was from an Audi dealer and was previously single owner. Mileage is currently 82k and bought at 72k. Just prior to purchase the ~70k service was performed. Do not have much for service prior to that but the car was clean. Hadn't had any motor issues until just recently.
As of a few weeks ago I got the CEL and it was the 16805/P0421 Warm up Catalyst: Bank1: Efficient Below Threshold. I cleared it a few times and after 50 or so miles each time it came back. Didn't affect performance from what I could tell. Over the last week I felt a performance drop after a really hot day in traffic so I chalked it up to the heat issue. However, the next couple days it seemed to have a slightly raspier exhaust tone and felt a little boggy at higher RPMs. Over the last week it has gotten worse. It still idles smoothly, but will show lack of performance in upper RPM range and it felt like misfiring/coils issues that i have had with previous Audis and VWs.
Now just the other a single Cylinder 2 misfire code registered. No other misfire codes however. I just moved the plug and coil pack from #2 to #3 and still issue with #2 only. Also, last night i noticed the CEL flashing at high RPMs but not at low RPMs. I also took a video last night at idle. I know of the high pitched ticking noise (injectors?) is normal in these cars but I swear i am hearing a little more deeper chatter than usual now. Am I hearing valve chatter? Or maybe just the intake flapper? Video shows just the passenger side of the IM but that is not on purpose. Chatter noise was coming from IM but no necessarily solely from either side that i could tell.
https://youtu.be/xxEZLQ09Xzg
I will be starting the typically troubleshooting items but i may not have the time to try to much as it is my DD. So i am now on the motorcycle hoping for sunny skies the rest of the summer.
thanks in advance
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