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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 > I think I know the cause of all misfires



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      01-24-2012, 04:41 PM   #1
tscdennab
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I think I know the cause of all misfires

If you noticed, for some months people are reporting misfires left and right. Most people still have misfires after changing the spark plugs. It all begun like 6-9 months ago.

I read some threads on this forum and other forums (unfortunately I'm not allowed to post the link to the other forum) regarding a tool which has lately been found to work for at-home injector coding (INPA), and all the people using the tool and having misfires reported the fact that the injectors were not correctly coded after the replacement. The tool indicated either wrong values or missing values for some injectors. Some people even reported incorrectly installed injectors: there is some kind of fastener/spacer missing at the base of the injector.

At the same time, the bulk of the misfire reports begun just after BMW started rolling out the injector recall.

So my conclusion is: the majority of the misfires are because the dealers incorrectly installed and coded injectors in the injector recall procedure. At stock boost, the incorrect coding may work, but at higher boost with tunes, correct injector coding and installation becomes critical.

Why wouldn't a dealer know how to correctly install an injector, you may ask yourself ? Because the N54 engine is one of the first BMW engines with direct injection and needing injector coding. Few new cars need injector work, so the majority of the injector work that the dealers do implies "regular" injectors (for older, non-direct injected engines) which I believe do not need any coding.

Luckily, I had all injectors replaced as per the recall and I don't have any misfires, but I did have a hard time to convince the service advisor that the injectors must be coded into the ECU after the replacement. He said that they only have to be coded in order for BMW to know which injectors you have...go figure

Just my $1.

Last edited by tscdennab; 01-24-2012 at 05:28 PM.
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      01-24-2012, 04:44 PM   #2
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http://www.e90post.com/forums/showthread.php?t=638610
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      01-24-2012, 04:59 PM   #3
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I have a hunch this may be the case as well. I took my car in for misfires a while back and they replaced an injector...don't recall which one. A few months and two demolished spark plugs later in the same cylinder (need to call up the dealer to see which one they replaced)...I am a bit suspicious. If it turns out my #2 injector was miscoded and I have some cylinder damage I am going to raise hell. It will be interesting how I prove all of this though.

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      01-24-2012, 05:18 PM   #4
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Extremely interesting...
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      01-24-2012, 05:32 PM   #5
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Might make sense. My car with old ass plugs at 31k with FBO + meth with no injectors ever changed has never misfired unless it was specifically procede related. Interesting theory.
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      01-24-2012, 05:33 PM   #6
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Quote:
Originally Posted by SlowerThanU View Post
If it turns out my #2 injector was miscoded and I have some cylinder damage I am going to raise hell. It will be interesting how I prove all of this though.
Use the cable to check the #2 injector values and compare them with the ones stamped on the injector. If they are wrong, do NOT touch them, go to the dealer and tell them that you believe the injector is not coded right and that's what's causing the misfires. And after the dealer codes the injector, order a compression test at the same dealer in the same day. If the compression test shows cylinder 2 damage, raise the hell.
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      01-24-2012, 05:35 PM   #7
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I think it's partially lazy mechanics AND that the BMW diagnostic systems are dog slow. They just want to turn and burn.

And one other guy reported that they forgot to put decoupling elements on his injectors, which makes them sit farther down in the combustion chamber. Just sloppy, lazy work if you ask me.
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      01-24-2012, 05:38 PM   #8
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Quote:
Originally Posted by tscdennab View Post
Use the cable to check the #2 injector values and compare them with the ones stamped on the injector. If they are wrong, do NOT touch them, go to the dealer and tell them that you believe the injector is not coded right and that's what's causing the misfires. And after the dealer codes the injector, order a compression test at the same dealer in the same day. If the compression test shows cylinder 2 damage, raise the hell.
And a borescope of the cylinder walls and piston crown.
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      01-24-2012, 06:46 PM   #9
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Quote:
Originally Posted by JamesM3M5 View Post
And a borescope of the cylinder walls and piston crown.
Will do.

Last edited by SlowerThanU; 01-25-2012 at 08:10 AM.
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      01-24-2012, 06:49 PM   #10
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Quote:
Originally Posted by tscdennab View Post
Use the cable to check the #2 injector values and compare them with the ones stamped on the injector. If they are wrong, do NOT touch them, go to the dealer and tell them that you believe the injector is not coded right and that's what's causing the misfires. And after the dealer codes the injector, order a compression test at the same dealer in the same day. If the compression test shows cylinder 2 damage, raise the hell.
Good plan.

I wonder if I put my last spark plug with two of the three electrodes missing back and let them figure that one out. Car was obviously misfiring pretty bad then.


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      01-30-2012, 09:18 AM   #11
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Originally Posted by SlowerThanU View Post
Good plan.

I wonder if I put my last spark plug with two of the three electrodes missing back and let them figure that one out. Car was obviously misfiring pretty bad then.

That's unacceptable. I'd be furious.
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      01-30-2012, 09:28 AM   #12
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I think it is pretty obvious to most techs that the N54 injectors (not N55) must be coded, as BMW made it pretty clear from the beginning with the recall instructions. I have been told the car might not even start if you try and run the car without coding the injectors.
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      01-30-2012, 09:38 AM   #13
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Quote:
Originally Posted by hotrod182 View Post
I think it is pretty obvious to most techs that the N54 injectors (not N55) must be coded, as BMW made it pretty clear from the beginning with the recall instructions. I have been told the car might not even start if you try and run the car without coding the injectors.
i run my car with 3 uncoded injectors for about 100 miles without any issues.
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      01-30-2012, 11:19 AM   #14
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Quote:
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i run my car with 3 uncoded injectors for about 100 miles without any issues.
When one of the pistons cracks the block and comes flying through the hood, snap a pic always wanted to see that
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      01-30-2012, 11:41 AM   #15
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After entering injector coding numbers the last couple might change due to math equations in the isid. It even tells you in the test plan. Very rarely will the numbers in the dme match to the code on the injector.
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      01-30-2012, 11:46 AM   #16
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After entering injector coding numbers the last couple might change due to math equations in the isid. It even tells you in the test plan. Very rarely will the numbers in the dme match to the code on the injector.
I have 4 out of 6 injectors that have their coding matching EXACTLY their stamping.
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      01-30-2012, 12:48 PM   #17
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I have 4 out of 6 injectors that have their coding matching EXACTLY their stamping.
lol i am not here to agrue with you. I am just saying due to math calibrations some will not match exaclty up. It even states it in the test plan. But you are right some do and some dont. I can see if all 6 numbers are off but if the couple are off its the math calibration.
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      01-30-2012, 12:48 PM   #18
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sorry i ment last couple are off liek the last 2 or 1 numbers in the 6 number code.
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      01-30-2012, 01:46 PM   #19
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I doubt this is the cause of misfires... may play into AFR stability though. Maybe smoothness at idle or cruising. But during WOT the tolerance is a minor compared to total fuel being injected.

DZ had no values entered... now that's a little weird and could have a bigger impact.
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      01-31-2012, 11:07 PM   #20
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I doubt this is the cause of misfires... may play into AFR stability though. Maybe smoothness at idle or cruising. But during WOT the tolerance is a minor compared to total fuel being injected.

DZ had no values entered... now that's a little weird and could have a bigger impact.
The last major service I had when I picked up the car, they rolled it out and it was misfiring badly. They kept the car overnight, re-coded the injectors (They did plugs, two injectors I think, fluids, brakes etc. the day before), and the next morning said it was fine, no big deal, here you go.

My rough, stumbling idle came back after that and hasn't gone away since, including a misfiring start a month later. Had to have roadside come pick her up. Got a couple new injectors to replace "clogged ones". Now 10k mi or so since, and still have rough idle.

Kind of nervous given end of warranty approaching.
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      02-01-2012, 12:30 PM   #21
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Quote:
Originally Posted by litz4244
sorry i ment last couple are off liek the last 2 or 1 numbers in the 6 number code.
Do you use DISv57 as well or do you have ISTA/D?

The test procedure I went through using DIS warned me that the last digits may not exactly match. It's normal like you said.
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      02-02-2012, 03:12 PM   #22
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Do you use DISv57 as well or do you have ISTA/D?

The test procedure I went through using DIS warned me that the last digits may not exactly match. It's normal like you said.
I use ista. But the dis does it to. When the conversion is done in the dme the math equation throws it off.
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