Weird engine miss

[tjtbelmont]

I just bought a 2007 RS4 a couple months ago. It is a super clean car and I love it but I am having a strange engine miss. Not the common random misfire that is from the coil packs. I did a carbon cleaning, replaced the injectors, changed plugs and coil packs. Runs great but when I stop at a light and the engine idles it sounds and feels like it drops a cylinder. No CEL, start driving and it is hard to clear up. If I shut it off and start it right back up the miss is instantly gone. I am waiting for my Vag- com to show up so I have not found which cylinder it is if it is even the same one all the time. If I bring the idle up a couple hundred RPM it usually doesn't happen. Reason I replaced the injectors was because it already had new coil packs so I figured with 120k it might have a dribbling injector causing it. I couldn't find anything on here that described a miss like this. Any one ever heard of anything like this?

[dolphinaudi]

My S4 had a miss at idle that ended up being an o2 sensor I believe, that was a long time ago so I'm going on memory. I think I did the plugs at the same time. You've kind of addressed all the typical things.

[tjtbelmont]

Thanks for the input. I believe I just found my miss. I pulled my oil pan to reseal it and found traces of coolant and what looks like stop leak? I would guess that some douche bag put it in so seal up the weeping head gasket. I had read on another post that a head gasket was the cause of another persons miss but I hadn't seen any signs until now. The joys of buying even bad ass used cars. Yay me! I get to pull an engine at Christmas. What does everybody recommend when it is out? Reseal everything, clutch, JHM shifter shaft and bushing? Anything else?

[VinnysS4]

Have you done the timing set? I know the RS4 doesn't have timing issues...but while you have it out...with 120k, might as well do it

[staypuft]

+1 on the o2 sensor ...

[wednesday]

Throttle body.

[tjtbelmont]

I just bought the car a month ago so don't know its service records. I intend on checking the timing tensioners when resealing, going to inspect the whole engine when its apart. Top o2 sensors are probably a must, thanks for that. what should be done with the throttle body? Car has been taken care of and has lots of goodies on it already. AWE cat back and down pipes, intake spacers, throttle body coolant bypass, etc. hopefully cylinders look ok when it comes apart. Rings are insane for this engine. Thanks for all the input.

[wednesday]

http://www.audizine.com/forum/showth...-body-problems

https://www.youtube.com/watch?v=OmxIKRuTRPA

[tjtbelmont]

Merry Christmas everyone! Unfortunately found my engine miss yesterday. Severely scored cylinder wall on d/s back hole intermittently fouling plug with oil. I'm screwed and cannot afford this. If anyone knows of a good deal on a block please let me know.