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Old 04-15-2019, 08:37 PM   #1
RacerFreddy
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APR K04 Misfires (A little different than the usual)

Quite the weird set of misfires from my K04 tune. I'm sure by now you've all seen the common problems and solutions, but mine is a little different and I can't figure it out. Nothing I log thru VCDS is really making it clear.

Low rpm, low boost runs normal.
Low rpm, 6th gear, high boost, like up to 20 lbs, still pretty normal.
Hit 3k rpm and up and boom, misfires like crazy on just cylinder 1, car goes lean and cuts fuel, pulls timing, the works. Can't get into the higher RPMs on throttle really at all.

Vagcom has shown me that my rail pressure doesn't vary too much, the fuel trim adjustment is like .8% so fueling is good, no issues with MAF that I can see which was the common problem on APRs tune. I can unplug it and no change. My P3 gauge shows good AFR's and boost isn't spiking to above 20 psi or so, like I've seen with bad wastegate adjustment.

Moved coils, checked plug gap, at about .025-.026 which is perfect it seems, until I get into the rpms. Is it possible to be a bad injector, can they be bad at higher rpms but work at idle and low load? I ruled out LPFP because it's only on one cylinder, I'd likely have rail pressure issues or widespread misfires.

Any maestros in here that might have some insight, I have a decent size log that I could provide, but aside from injector timing going to zero during the misfires, aka pulling fuel, nothing seems off in there.
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Old 04-15-2019, 10:47 PM   #2
RacerFreddy
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Seemingly solved it a few minutes after posting, oddly, a throttle body alignment fixed a lot of the issues. Then I blew the throttle body pipe off, will get another chance to drive it tomorrow morning, so we'll see.

Definitely odd, I knew having removed the manifold that this would have to be done, but never would I have expected it to cause that much issue. I still don't know why it focused so badly on cylinder 1.
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Old 04-16-2019, 11:01 PM   #3
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After another day of driving it still does it but not as bad. Seems like full throttle fixes it a bit, and AFRs drop to 10.8-11.0 or so, but still misfires and gets a bit of that pull, stutter, pull feeling.

Boost comes on quickly, climbs to normal levels, spikes to 22-23 which is perfect. Seems everything turbo related is still good, but maybe spark or fuel is still not keeping up, hard to say.

Time for more logging.
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Old 05-19-2019, 07:22 PM   #4
DeepBlue
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Had similar symptoms happen twice, years apart. Both instances were fixed by coil pack replacement. They were not worn or anything, but my car is heavily modified. They just blow up from from time to time.
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Old 05-26-2019, 01:09 AM   #5
ROH ECHT
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If you know the coil, plug, and injector are good..it may end up being a failing roller-rocker, sticky lifter, or valve.

Or; Carbon cleaning of the intake valves may resolve it as well.

Or; Damaged coil wiring or connector to that cylinder's coil is another possibility.

Given vcds reveals nothing other than the misfiring, and isolated to the one cylinder, it will likely be mechanical.
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