Hello and thank you for what you do. Love your channel. I’m at the end of my rope with this car. Long long story short. I bought this 08 Audi S5 manual trans sight unseen for a very low price because it had misfires on 4 and 7. After digging in I found that the 1 cylinder rocker arm fell off the intake valve. Instead of messing with it I bought a 60k mile engine and had it swapped. The shop quoted 2,700 and the final bill was 5,600 when I told them to stop and have it towed back to me. It still had a misfire on 4 and 7. Changed all coils, plugs, injectors and did a carbon clean on the valves. No change. I replaced the engine wiring harness and now it sputters at idle and the check engine comes on but if I bring the RPMs up to 2000 it’s smooth and the engine light turns off. Then back to idle and its back to sputtering. Sometimes it will sputter idle and not throw codes but when it does it’s P0300, 304, 305, 307. The exhaust smells very strong (don’t know if that’s relevant). Any advice or suggestions would be greatly appreciated! Unless you’re going to say part it out lol
Thank you!
Jason
Check the FAQ on this forum regarding misfire.
Ahhh, quite a project ya got there. So you got random misfire, but has replaced the whole engine and wiring harness. Since you don't want to part out, here are my 2 cents. First if you are mechanically inclined, re-evaluate all prior work done. Double check that everything is in its right place and where it is supposed be torqued down or otherwise. Then from there do the tests, smoke, leak down, compression tests. Then if you haven't figured it out, move down the line of air, fuel and spark and computer. I know that Audis of your generation have major issues with their intake systems so if it is sputtering ONLY at idle then check throttle body and pray it ain't the manifold or plenum that is kaput. You in for pain if you haven't done it before.
