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Author Topic: Frustrating misfire  (Read 7287 times)
AARDQ
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« on: October 10, 2014, 05:01:52 PM »

BEL 2.7T in an A6.  FTs, 2.5" downpipes with cats but stock mufflers.  Bosch V-8 MAF.  46-lb Ford Racing/Bosch injectors.

Been battling this for a while, but not able to solve misfire cylinder 1.  New BRK7Es, tried gaps from 0.028 down to 0.020 (actually seems best at 0.028)  Also tried Bosch F5DP0R side electrode, no help, maybe actually worse.  Tried 07K-905-715F 2.0 TFSI coils, which helped a fair amount.  Connector looks fine, no tracking or arcing that I can see.  No oil in the plug well.  Replaced the injector with a spare also.  Condition is worse, much worse, in hot weather.  Tried various AFRs as low as 10.5 and as high as 12.5  Fueling looks like it's tracking fine (14point7 installed in Bank 1/passenger's side and feeding the ECU).  Rarely misfires at all during 1st and 2nd gear pulls.

Compression is a uniform 135 psi (corrected to sea level; actual is a uniform 105 psi but I'm at 6,200' so 22% reduction) and uses virtually no oil (2500 mi to a quart).

Despite the fact that the engine seems fine except for this, I'm coming to the conclusion that something mechanical is heading south.  Before I go looking for a flat cam lobe or something, does this sound familiar to anyone?  I see that cylinder 4 also misfired a time or four this time around, so maybe it's a flow condition of some sort?

3rd gear log attached, and thanks in advance.
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terminator
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« Reply #1 on: October 16, 2014, 08:17:15 AM »

I know some Allroads with misfires and the problem with cylinder head.
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AARDQ
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« Reply #2 on: October 16, 2014, 08:34:42 AM »

I know some Allroads with misfires and the problem with cylinder head.

Interesting.  What's the issue?

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goatman
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« Reply #3 on: October 16, 2014, 05:11:36 PM »

BEL 2.7T in an A6.  FTs, 2.5" downpipes with cats but stock mufflers.  Bosch V-8 MAF.  46-lb Ford Racing/Bosch injectors.

Been battling this for a while, but not able to solve misfire cylinder 1.  New BRK7Es, tried gaps from 0.028 down to 0.020 (actually seems best at 0.028)  Also tried Bosch F5DP0R side electrode, no help, maybe actually worse.  Tried 07K-905-715F 2.0 TFSI coils, which helped a fair amount.  Connector looks fine, no tracking or arcing that I can see.  No oil in the plug well.  Replaced the injector with a spare also.  Condition is worse, much worse, in hot weather.  Tried various AFRs as low as 10.5 and as high as 12.5  Fueling looks like it's tracking fine (14point7 installed in Bank 1/passenger's side and feeding the ECU).  Rarely misfires at all during 1st and 2nd gear pulls.

Compression is a uniform 135 psi (corrected to sea level; actual is a uniform 105 psi but I'm at 6,200' so 22% reduction) and uses virtually no oil (2500 mi to a quart).

Despite the fact that the engine seems fine except for this, I'm coming to the conclusion that something mechanical is heading south.  Before I go looking for a flat cam lobe or something, does this sound familiar to anyone?  I see that cylinder 4 also misfired a time or four this time around, so maybe it's a flow condition of some sort?

3rd gear log attached, and thanks in advance.


Are the injectors ev14 or ev1
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AARDQ
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« Reply #4 on: October 16, 2014, 06:26:30 PM »

EV 14.

Not quite convinced that this is fixed, but changing my ecu out for my spare (same file) has really helped.  No misfires until 6,700 rpms now, instead of 5,800, and only occasional. Jury's still out, but a couple of days after making the switch, it's much, much better if not completely solved.

Found something interesting, on high-load/high rpm shift, until the clutch switch picks up (I think this accounts for the delay; haven't researched), coils will continue to fire.  Until the clutch switch picks up, the ECU doesn't know you are shifting and thinks you are in a high rpm/low load situation.  When you complete the shift and get back on the throttle, dwell comes back in wherever it was when the clutch switch picked up.  If you have low dwell entered in high rpm/low load cells of KFTSRL, as I did, you will get a misfire once you get back on the throttle.
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