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      07-08-2019, 04:57 PM   #1
ThatOneN54
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Help! Misfires! ive tried everything... I think

To get started, I have a 2008 BMW 135i(N54) with about 30,000 miles. The car does have a doc race single turbo kit install.

So, the issue is I cant seem to get the car to stop misfiring. At first I was under the impression that it was because of the o2 sensors since single turbos seem to burn though those pretty frequently and I was also getting o2 related codes. I replace both primary and secondary o2 sensors. I no longer have codes related to 02 sensors but now misfire code in cylinder 6.

The next thing that was done in order to address the misfires was replacing the spark plugs. I Replace the Bosch plugs with NGK 2 - step colder plugs and gapped them to .020. Still getting misfires in cylinder 6.

When pulling the old plugs, plugs from cylinder 3 and 4 smelt like fuel and had fuel on the threads. With this in mind, I replaced my index 8 injectors with a set of new index 12 injectors.

Still getting misfires! The car drives fine at times then all of a sudden the misfires begin. Initially only cylinder 6 was misfiring but recently ive also received codes for misfires in cylinders 1 and 5. Additionally the car does have Precision Raceworks coils installed and has had the intake ports walnut blasted. Still misfiring. Could this be an issue with the HPFP?The car hasn't had any issues starting up which leads me to believe that the misfires aren't related to the HPFP. Then again what else could it be? Any ideas??

PLEASE HELP!!!
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      07-08-2019, 10:23 PM   #2
JM98
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Quote:
Originally Posted by ThatOneN54 View Post
To get started, I have a 2008 BMW 135i(N54) with about 30,000 miles. The car does have a doc race single turbo kit install.

So, the issue is I cant seem to get the car to stop misfiring. At first I was under the impression that it was because of the o2 sensors since single turbos seem to burn though those pretty frequently and I was also getting o2 related codes. I replace both primary and secondary o2 sensors. I no longer have codes related to 02 sensors but now misfire code in cylinder 6.

The next thing that was done in order to address the misfires was replacing the spark plugs. I Replace the Bosch plugs with NGK 2 - step colder plugs and gapped them to .020. Still getting misfires in cylinder 6.

When pulling the old plugs, plugs from cylinder 3 and 4 smelt like fuel and had fuel on the threads. With this in mind, I replaced my index 8 injectors with a set of new index 12 injectors.

Still getting misfires! The car drives fine at times then all of a sudden the misfires begin. Initially only cylinder 6 was misfiring but recently ive also received codes for misfires in cylinders 1 and 5. Additionally the car does have Precision Raceworks coils installed and has had the intake ports walnut blasted. Still misfiring. Could this be an issue with the HPFP?The car hasn't had any issues starting up which leads me to believe that the misfires aren't related to the HPFP. Then again what else could it be? Any ideas??

PLEASE HELP!!!
Do you have any logs?
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      07-09-2019, 11:03 AM   #3
ThatOneN54
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Ive attached the log. This log show a 3rd to 4th pull. During this pull the SES light came on as well as codes for misfires in cylinder 5 and 6.

Additionally, I did a compression test today and it was about 180 psi across all cylinders.
Attached Files
File Type: zip 2019-07-09 07_35_22 Map-1.zip (3.5 KB, 15 views)
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      07-09-2019, 02:34 PM   #4
BimmerAg
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Do you have a log with fuel rail pressure? In the log you posted, your low-pressure fuel pump looks like it starts to struggle a bit at higher RPMs. Pressure drops from a steady 65 psi down to about 47 psi right before you shift. I'm not an expert, but I could see that causing the HPFP pressure to drop and cause misfires.
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