How to check wiring to coils? Tracking down high rpm misfire in one cylinder

[gesTTalt]

I need to check one of my coils is receiving signal. I'm chasing down high rpm misfire in cylinder 6. Things I've tried already:

Swapped coils, but misfired stayed. These are new coils.
Changed the plug - looks darker, like sooty compared to my other plugs.
Injectors are all cleaned and tested
ST and LT fuel trims look good

Symptoms started a couple of weeks ago after doing some runs. Misfire only happens at high rpm or wot. I just put the car back together after cleaning the injectors, and they were pretty dirty. All is good now. I should have swapped cyl 6 injector, but since they were cleaned, didn't think I needed to switch it.

I'll be doing a compression test this weekend, as well as reducing the gap in the cylinder. When I have time, I will also do a carbon clean (about 15k since last carbon clean)

I have a volt meter, wondering what I should be looking for?



UPDATE 4/1/16

bumping this, hoping to get more input. Misfire started weeks ago when doing some runs with friends. Misfire in Cylinder 6 continues, only at WOT or heavy load past 4500rpm

Here's what I've done:

New coils, even swapped cylinders 1-4 with 5-6
New spark plugs, gapped smaller from .0032 to .0026
Cleaned and flow tests injectors
ST and LT fuel trims look good still
HP fuel at rail is at requested at WOT
Compression, with enige slightly warm from moving the car, is at 170 across all cylinders

I have not carbon cleaned since 80k, now at 96k. Last thing I can do is carbon clean, which I can't do for a couple of weeks.

Car runs fine at part throttle. No DTC other than the misfire in Cylinder 6. I can keep the DTC from logging if I don't go WOT. Also, can rev past 4500 rpm without setting of the misfire, so long as I am not going WOT. It does not misfire in any other cylinder.

[MugelloB7RS4]

Are you getting any codes?

[gesTTalt]

I can make it throw a misfire code if I go wot enough. Car is drivable without going wot or staying above 4500 rpm. I don't want to cause any damage with it misfiring. I don't think is leaning out, which is good.

[lucidmatt]

Is it a random misfire or is it consistently in one cylinder? Edit: saw cylinder 6. If you have access to Vagcom you can log fuel trim and spark advance, that might help if you have access to a vagcom. Although I'm not much use with wiring. Never liked it.

[gesTTalt]

Bumping for any other input. I updated the top thread

[FWP!]

Any codes in VCDS?

Do some runs and log fuel rail pressures. I had to replace my HPFP's after getting a misfire at anything more than partial throttle.

[gesTTalt]

Any codes in VCDS?

Do some runs and log fuel rail pressures. I had to replace my HPFP's after getting a misfire at anything more than partial throttle.

HP fuel rail pressures requested and actual are spot on. Aside from the misfire DTC, nothing else. I can keep the DTC from logging as long as I don't go WOT for too long.

Misfire in Cylinder 6 continues, only at WOT or heavy load past 4500rpm

Here's what I've done:

New coils, even swapped cylinders 1-4 with 5-6
New spark plugs, gapped smaller from .0032 to .0026
Cleaned and flow tests injectors
ST and LT fuel trims look good still
HP fuel at rail is at requested at WOT
Compression, with enige slightly warm from moving the car, is at 170 across all cylinders

I have not carbon cleaned since 80k, now at 96k. Last thing I can do is carbon clean, which I can't do for a couple of weeks.

Car runs fine at part throttle. No DTC other than the misfire in Cylinder 6. I can keep the DTC from logging if I don't go WOT. Also, can rev past 4500 rpm without setting of the misfire, so long as I am not going WOT. It does not misfire in any other cylinder.

[komseh]

gesTTalt, I'm thinking it may be a problem with the injector in cylinder 6 since the misfires are only happening at WOT. Maybe the injectors were not tested at the correct duty cycle that would be experienced during WOT. The injectors at WOT should be at 80-90% duty unless the tune with your blower is causing them to push beyond that.

Can you scope the cylinder to rule out strange carbon buildup or cylinder wall damage first? Be careful with your testing, WOT is the worst time to have misfires going on.

Edit: I guess that seems unlikely given you didn't have any misfires before and you only had these injectors cleaned. Seems like a tough problem to troubleshoot.

[gesTTalt]

gesTTalt, I'm thinking it may be a problem with the injector in cylinder 6 since the misfires are only happening at WOT. Maybe the injectors were not tested at the correct duty cycle that would be experienced during WOT. The injectors at WOT should be at 80-90% duty unless the tune with your blower is causing them to push beyond that.

Can you scope the cylinder to rule out strange carbon buildup or cylinder wall damage first? Be careful with your testing, WOT is the worst time to have misfires going on.

Edit: I guess that seems unlikely given you didn't have any misfires before and you only had these injectors cleaned. Seems like a tough problem to troubleshoot.

I'm troubleshooting all the possible scenarios. I'll get a new injector when I carbon clean and see if that will remedy the problem. After the carbon clean and new injector, I may need to get some help.