BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > General E90 Sedan / E91 Wagon / E92 Coupe / E93 Cabrio > N54 misfires and rough idle only on cold start and when temperature is cold outside

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      02-10-2023, 03:38 AM   #1
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Unhappy N54 misfires and rough idle only on cold start and when temperature is cold outside

Before anyone says anything, I have read the millions of posts already in the forum and I've tried nearly everything. Below I will explain my situation and what I've tried.

A couple months ago I started having misfires in cylinder 2, pulled the injector and my bore was damaged so I used an injector bore repair kit to repair the bore. After installing this kit, I was still getting misfires. It evolved into misfires across all of bank 1. Cylinder 1,2,3. Only on cold start. To this day even after everything I've tried, I am still having misfires on cold start.

Below is what I've tried:
I replaced injectors with all index 12 and 11.
all new spark plugs (step 2 colder gapped to 0.021)
swapping around coils (precision raceworks coils)
leak testing all injectors (no leaks)
compression testing all cylinders (all about 150-165, tested both cold and warm)
I'm running PI and full e85 so intakes are clean

More recently I had O2 sensor failure codes pop up for the first time after months of dealing with this issue with no definitive answer to what's causing it.

I replaced bank 1 post cat and pre cat O2. And after all this I am still getting misfires on all of bank 1 and only bank 1. And only on cold start, or sometimes after I do some heavy pulls.

Getting no codes other than misfire codes and like I said, more recently O2 sensor failure codes
Appreciate 0



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