High RPM misfires

[Jsalicru]

Hey everyone. Want to see if you all can help me identify the issue at hand here.

Have a 07 RS4, 110k on the odometer.

Generally runs very well but I suddenly started getting misfire CELs (flashing and solid). Generally it’s for Cylinders 7 or 6.

It’s likely that the car is at a point where it might need a carbon clean and I am already assembling the tools and parts necessary for the job.

I’ve already replaced the plugs with OEM plugs. The plugs that were in there were also OEM and seem in pretty good shape.

Mod-wise it’s only a resonator delete. X pipe. And plugged vacuum lines for the exhaust valves. I’ve already checked to see if reattaching the lines to the valves remedies the problem but no.

Also, I should mention a few more things.
-The misfires always start >5700 rpms
-partially letting off the throttle seems to improve the issue
-it will randomly run perfectly and super strong.
-valve covers seem to be leaking a little oil. But it’s on both sides.

I have VAG-COM and I am also a fairly knowledgeable person when it comes to mechanics, etc.

Perhaps you could point out the best channels to log on VAG-COM to diagnose?

Sorry. A bit long. Any help is appreciated.


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[ven0m]

What is the status of your fuel injectors? Might consider accelarating that carbon clean and also add new injectors into the process.

My best guess is carbon, injector, bad O2 or vacuum leak. (the last 2 would affect a whole bank or would amplify a smaller issue on 2 individual injectors). Start searching here:

http://www.audizine.com/forum/showth...or-Maintenance

Diagnosis
Fuel trim data is a good place to start if you think your injectors might be clogged. Look at VCDS measuring block 032, which shows your long term fuel trims at idle and load. Short term fuel trim can be monitored in block 033.

A clogged fuel injector will inhibit optimal fueling in the motor. The ECU will see this lack of fuel over time using the O2 sensors and call for a permanent fuel trim correction. Looking at measuring block 032, a clogged fuel injector will cause a positive number to show up in the Partial field(Partial means at load). In my case it was showing between +5% and +6%. While these numbers are in spec, we really don't want to be running lean. Lean conditions are bad for engine performance and safety.

If you have positive long term fuel trim at load(block 032 Partial field), you can be fairly certain your fuel injectors are not flowing optimally if your car meets the following conditions:
Good O2 sensors - Bad O2 sensors can cause inaccurate fuel trim readings
Good fuel pressure on both banks - Check measuring blocks 103, 106, 140
No vacuum leaks - Check the Idle field in block 032, it should be slightly negative in a good condition.
Normal short term fuel trims - Your short term fuel trims need to be within +/- 10%

[Seattle squash]

Hey everyone. Want to see if you all can help me identify the issue at hand here.

Have a 07 RS4, 110k on the odometer.

Generally runs very well but I suddenly started getting misfire CELs (flashing and solid). Generally it’s for Cylinders 7 or 6.

It’s likely that the car is at a point where it might need a carbon clean and I am already assembling the tools and parts necessary for the job.

I’ve already replaced the plugs with OEM plugs. The plugs that were in there were also OEM and seem in pretty good shape.

Mod-wise it’s only a resonator delete. X pipe. And plugged vacuum lines for the exhaust valves. I’ve already checked to see if reattaching the lines to the valves remedies the problem but no.

Also, I should mention a few more things.
-The misfires always start >5700 rpms
-partially letting off the throttle seems to improve the issue
-it will randomly run perfectly and super strong.
-valve covers seem to be leaking a little oil. But it’s on both sides.

I have VAG-COM and I am also a fairly knowledgeable person when it comes to mechanics, etc.

Perhaps you could point out the best channels to log on VAG-COM to diagnose?

Sorry. A bit long. Any help is appreciated.


Sent from my iPhone using Tapatalk

Like Venom said. Additionally, I had the exact issue only triggered at high rpm and went away with a carbon clean. Also, the injectors are a good thought and I had one fail open and hydrolocked the cylinder... no damage but pretty scary could have done some serious damage as I would consider doing injectors soon to be safe. And this one failed with a manic maintenance schedule and me only running 92/93 octane equivalent of euro 95/98. Good luck!


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[Jsalicru]

These are exactly the types of responses that I was hoping for. Thank you gentlemen. I am going to try and move up the schedule for the carbon clean as I already have the adapter

I will likely look into logging that channel and seeing the output.

Any more input is always welcomed :)


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