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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Yet ANOTHER persistent cylinder 5 misfire N54



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      08-28-2012, 12:38 PM   #1
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Hey all,

I have a car in the shop now with the same persistent cylinder 5 misfire under load (fine at idle and cruise). Easy to replicate the misfires, 3rd or 4th gear, 2500-3500RPM full throttle. It revs through the misfires and accelerates (albeit slowly since it's stock) all the way to rev limit with little drama. Takes several pulls in 3rd/4th to finally set the SES light and cylinder 5 shutoff.

E93 335i 6MT, 36k miles, no tune, all stock. New BMW Bosch plugs. New coil on cyl 5.

1) Swapped coils 5<->4, customer has already installed a new coil on 5 previously.
2) Swapped injectors 5<->6, misfire on cyl 5 still. Decouplers on both injectors, seals look fine, these are probably replacements from when the car was still under warranty. Tips of injectors looked dirtier than others I've seen but not terrible.
3) Injectors coded properly in ECU
4) Car does not have injectors that qualify for warranty replacement
5) Checked wiring and ECU connections, no issues found.
6) Injector bore and step for the decoupler element look perfect - no galling, damage, or trouble visible. No metal-to-metal contact found on the tip of injector 5.

Codes:

2AAF Fuel pump plausibility - intermittent, no low pressure fuel system problems found.
2D18 Tuning Protection (Air mass flow max - tuner code, don't know why since it's all stock, hasn't come back on 3 test drives, though)
29D1 Combustion misfires cyl 5, with cylinder shutoff
2F81 Engine Switchoff time, damaging exhaust gas
2F83 Engine Switchoff time, no matching fault symptom

Next step is to bore-scope the cylinder and maybe check for extreme carbon build-up in the intake. Have to get further diagnostic time approval from customer, will continue to update the thread...
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      08-28-2012, 12:45 PM   #2
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It might be the DME like others have been reporting lately.
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      08-28-2012, 12:51 PM   #3
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wow sucks man....
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      08-28-2012, 01:05 PM   #4
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dat boost doe
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Quote:
Originally Posted by Richurd View Post
It might be the DME like others have been reporting lately.
whats going on with the DME?
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      08-28-2012, 01:14 PM   #5
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Quote:
Originally Posted by hemi to e90 View Post
whats going on with the DME?
some are starting to fail
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thanks to MGallop
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      08-28-2012, 01:29 PM   #6
hemi to e90
dat boost doe
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Quote:
Originally Posted by Dmacc View Post
some are starting to fail
ooooo fuck
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      08-28-2012, 04:45 PM   #7
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I think I found it!

Possible DME software issue, BUT, I think the DME is recording misfires on the WRONG CYLINDER.

So the customer said he replaced (or had them replaced) the spark plugs. He was very smart in labeling each one and saving them once removed. #1 was sooted up around one half of the side of the plug, the rest were just worn and normal looking.

Lo and behold the NEW #1 plug looked VERY SOOTY around 1/2 of the side of the plug. Interesting, eh? Borescope in the cylinders shows nothing conclusive, BUT you can see the tip of the injector protruding into the combustion chamber. #1 injector tip was very sooty as well, while the others were relatively clean.

So I swapped #1 injector, coil, and spark plug into different cylinders each and test drove again. The problem is not gone but much better. The sooty #1 injector tip is still sooty, and the plug that goes with that injector was also starting to get very sooty. The plug that was originally next to injector #1 was nearly burned clean again.

So I think the DME is falsely reporting the misfire on #5. I think it is a bad injector, and it's in cylinder #1. I will update with pics in a bit...
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      08-28-2012, 04:55 PM   #8
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wow very possible !!!!
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      08-28-2012, 06:30 PM   #9
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James, valve cover gasket maybe?

Especially if you're seeing buildup on the plug electrode or threads.
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      08-28-2012, 09:09 PM   #10
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Quote:
Originally Posted by themyst View Post
James, valve cover gasket maybe?

Especially if you're seeing buildup on the plug electrode or threads.
Possible but doubtful. Car only has 36,500 miles, but is a 2008 build. No leaks, nothing else funny about it, all stock. It's out of warranty now, so thankfully he didn't take it to the stealer.

I think the sooty buildup is poor fuel combustion, not oil. The piston crowns look pretty clean on large portions, and they look relatively the same across the 4 out of 6 I looked at. The plug is sooty around the area that is directly adjacent to the injector. I'll shoot some photos.

If this doesn't work tomorrow, we will have to pull the intake and/or do some leakdown testing.
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      08-28-2012, 11:50 PM   #11
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Quote:
Originally Posted by JamesM3M5 View Post
Possible but doubtful. Car only has 36,500 miles, but is a 2008 build. No leaks, nothing else funny about it, all stock. It's out of warranty now, so thankfully he didn't take it to the stealer.

I think the sooty buildup is poor fuel combustion, not oil. The piston crowns look pretty clean on large portions, and they look relatively the same across the 4 out of 6 I looked at. The plug is sooty around the area that is directly adjacent to the injector. I'll shoot some photos.

If this doesn't work tomorrow, we will have to pull the intake and/or do some leakdown testing.
My valve cover gasket leaked in cylinder 6 at 32k miles so anything is possible. Hopefully that's not the issue cause it's extremely time consuming to do that job.
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      08-29-2012, 08:44 AM   #12
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subscribed for this
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      08-29-2012, 06:32 PM   #13
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Quote:
Originally Posted by themyst View Post
My valve cover gasket leaked in cylinder 6 at 32k miles so anything is possible. Hopefully that's not the issue cause it's extremely time consuming to do that job.
FAIL.

Replaced the suspected bad injector and updated the stock software to the latest BMW version - no improvement. All new seals and decoupler elements on all the injectors I moved around, all coded properly. Also cleaned the MAP sensors, and both had oil all over them.

The only "improvement" so far is that the SES light isn't coming on and it is not shutting down a cylinder due to misfires. This, however, also means that it is not setting a code for misfires, and no amount of driving while misfiring will get it to tell me which cylinder is crapping out on me. The damn misfire monitors are turned down so low on the BMW tuning, and it makes for difficult troubleshooting at best. All the other non-turbos have misfire counters for each start cycle, and it will set codes much easier when transient misfires do occur. Really helps diagnose bent valves on all the older M50/M54/S54s that get an accidental mis-shift that barely nicks the valves, since they misfire lightly on cold start once you bend a few valves. Not so in these damn N54s.

So - next week we agreed to bring the car back and pull the intake for a carbon clean and inspect for excessive oil. I also advised that we will need to check the valve cover and gasket. Testing the PCV system via water manometer will let me know whether the whole cover needs to be replaced or just the gasket. I think there's a lot of oil getting into the intake, and myst is probably onto something here.
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      08-29-2012, 07:16 PM   #14
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Quote:
Originally Posted by m3alabama View Post
Sorry but sounds like a dealer is needed at this point for their expertise.
A dealer is not going to have more expertise on the N54 than James!

Further, rather than seeking to diagnose the problem, they'd be far more likely to just keep throwing on new parts -- without regard to cost -- until the problem disappears.

Neil
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      08-29-2012, 07:20 PM   #15
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How's the compression? I didn't see that anywhere in the original story. I've seen a few broken valve springs as well as a couple slight mis shifts that caused the rocker levers to pop off to one side of the can lobe. The cars both had good compression but it took longer to build the peak number. Removing the valve cover exposed that issue.
Another thing to check on the injectors is the presence of soot or build up on the top side indicating leakage in the head around it. Make sure that the holddown straps for the injectors are facing the right direction. One installed upside down can allow the injector to move as well and cause your issue. Keep us updated
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      08-29-2012, 09:18 PM   #16
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I haven't been too eager to get into the leakdown or compression for a few reasons. The owner has not mis-shifted (or hasn't admitted it? I'll ask more directly), the engine starts up hot or cold with no misfires, runs just fine everywhere else except 2500-3500. Past that it runs to redline with no hesitation. There has to be some sort of perfect storm going on in the midrange.

Dealer expertise. That's a new one I haven't heard.
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      08-29-2012, 10:09 PM   #17
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Definitely double check the hold down straps installation. As you are well aware, that's the peak boost window on the N54 and the highest load as a result. If that checks out okay and you're hesitant to want to pull the valve cover, try swapping a known good set of coils and plugs from another car. Injector misfires are usually on cold start in my experience. The mileage seems to be low for excessive carbon build up I cause a misfire. It's more likely you got a bad part off the shelf than extreme carbon build up.
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      08-30-2012, 11:11 AM   #18
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Quote:
Originally Posted by Bmw135er View Post
Definitely double check the hold down straps installation. As you are well aware, that's the peak boost window on the N54 and the highest load as a result. If that checks out okay and you're hesitant to want to pull the valve cover, try swapping a known good set of coils and plugs from another car. Injector misfires are usually on cold start in my experience. The mileage seems to be low for excessive carbon build up I cause a misfire. It's more likely you got a bad part off the shelf than extreme carbon build up.
Those straps are definitely oriented properly. I had 1, 2, 5, and 6 out, and the bow for 3-4 is definitely correct. There's no signs of the injectors rattling around, trading metal, or damaging the injector seal bore or the step on which the decoupler element sits.

Bad part is possible, but before the car first came in, the problem was persistent on cylinder 5. New plugs from BMW, still on cyl 5. New coil on cyl 5, still misfires on 5. Then the customer brought it to us. So I did my own tests, moved coil, plug, and injector. The misfire was still persistent on 5. After moving all that stuff around, finding the sooty tip on injector #1, replacing that injector, and putting it all back together with all the proper new seals and decouplers, etc, now it doesn't want to set a code for misfires, even though they're painfully apparent.

I think the VC gasket or whole VC plus the regular maintenance of intake intake cleaning is the next best step. Checking leakdown and compression will be a snap at that same time, too, so I'll definitely check that.
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      08-30-2012, 11:19 AM   #19
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Try resetting ALL adaptions in the DME? Seems to be the answer to alot of peoples problems when all else is done.
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      08-30-2012, 11:22 AM   #20
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Try resetting ALL adaptions in the DME? Seems to be the answer to alot of peoples problems when all else is done.
I didn't put that in the post, but that was also done. No help.
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      09-04-2012, 07:42 PM   #21
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So I had a slight miss under load, not enough to throw a ses light. Finally threw a code and went into limp mode.

I changed all the plugs, all looked very clean (27k miles). Took her out, another ses light, read the code and misfire on number 5. Swapped the coils around and miss still on cylinder five. Took it to the dealer to check the injector out, they swapped them around and still miss on five. They boroscoped it and found excessive carbon on the intake valves.

Only 27k miles and I have carbon issues? Cleaning not covered by CPO so all out of pocket, ouch. I just installed a oil catch can but doubt it helps that much in the future.
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      09-04-2012, 08:22 PM   #22
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