S6 carbon cleaned. Now if

A6 All/ S6 All
#21

The good news is it is confined to the one cylinder. If that is the case and I know you don’t want to hear this. But pull the injector out and swap the number 8 with the number 4. If the misfire goes to number 4 that tells you everything you need to know.

If you want to take a step before that. Do a comp test and see what the entire bank comes back with. But since we all know injectors are such a big deal on these cars and misfires are almost always in part injector related. It would be the best place to test.

The JHM TCU tune. I had it for my B6 a lot time ago. Very impressive. It really helps wake up the transmission as that is the next detuned part of the car. JHM unlocks the ECU up till the point where the TCU steps in and pulls back power.

I know JHM is releasing the TCU tune soon if it isn’t already out in beta testing for the S6 and S8

#22

I replaced all of the injectors not even 10k miles ago with the JHM flow matched injectors.

#23

Just for the sake of testing it would be best to try moving the injectors and see. You might see carbon collection on the tips.

Did you use media blast to carbon clean or chemical.

#24

pulled out the spark plugs for #6 7 and 8 today and checked the gap. All seemed fine but I’m still having misfire issues. Today got a code misfires on 6 and 8. Everything seems the worst when the engine is cold. I’m getting super stumped on this. JHM flow matched injectors, new spark plugs and new coils all fairly recently. I don’t get why this engine is misfiring. The passenger side bank of cylinders is fine. Any ideas on what I can check next? I’m not thinking this is an injector issue currently since the car cruises fine. I don’t know if I maybe have a vacuum leak or what. My long term fuel trims seem out of whack. Any ideas where to go next?

When I did the carbon cleaning I used chemicals. No media blasters.

#25

Drove the car some today. As the car warms up it misfires less and less on cylinder 8. But it’s still counting a lot of misfires even when the engine is warm.
I watched the misfire counter on VCDS and when the car idles it misfires on 8 but when I add in some throttle it stops misfiring. Cruising down the road it’s not logging any misfires. Not totally sure if it’s actually not misfiring while cruising or it’s just not being picked up by the computer.

Still lost on why it’s doing this.

#26

So I’ve ordered a compression checking tool to see if cylinder #8 is having issues. If it checks out then I’ll take the intake off and replace the injector with a new Hitachi one. Kinda hoping its the injector at that point. I replaced all of them awhile back with JHM flow matched injectors so maybe one of them is crapping out.

#27

Got everything put back together this morning. Cleaned all the valves again … i think this is the 4th time now. Replaced the injector on cylinder 8. Had the 5 injectors out on cylinders 6-10 and ran the tip of each injector through my ultrasonic cleaver. So far the car is running 100% better. Not getting my hopes up fully yet because it always seemed to run better after the battery has been disconnected for awhile.
Before cylinder 8 would misfire constantly. Occasionally it would throw a code. Now I don’t get any misfire counts when I am connected into VCDS. Let’s hope it stays that way. The injector that was bad was one that JHM had cleaned and flow matched. I installed ten of them exactly two years ago. I guess even though it checked out good with them (JHM) it still is a used injector in the long run.

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