2003 Z4 E85 Misfire on Cylinder 2 driving me nuts!

Z4LauncherMan · Post by **Z4LauncherMan** » Tue Jan 31, 2023 1:18 am

Hey Everyone,

I am wondering if anyone can help me. A few weeks ago I purchased a 2003 Z4 3.0 with 6 speed manual. Its a nice car. The car has only 56,000 miles (not bad for 20 yr old car). Anyway, it was a 1 owner car as well and was fairly well kept up. I have all of the records, etc.

That said, I have driven it a few times and decided it probably was best to do an oil change, air filter change, etc. Basically get it all done so I know how long before next interval. After performing the maintenance, I randomly got a service engine soon light on the dash when I cold started it one morning. I have a fairly advanced scan tool and it is giving me a misfire on Cylinder #2 (P0302).

I then went into fix mode and replaced all 6 spark plugs with NGK OEM. I also replaced the Ignition coil on Cylinder #2 to a new one. I still got the code after doing so. Then I proceeded to pull all the fuel injectors and clean them- while also replacing the #2 injector with a brand new OEM siemens one. To my dismay I am still getting the same code. Whats odd is it ONLY happens when the car is fairly cold- after sitting a while or overnight. I also can see the RPM gauge has a slight jitter. Not a bad one, but very slight (maybe 50-75 RPM jump). I can also slightly feel it in the manual shifter knob. I am not sure what is normal for these cars. I have also removed the air intake and checked for cracks- it looks very clean with no signs of splits anywhere.

Any ideas? I love this car but am baffled at what this issue could be.

javis20 · Post by **javis20** » Tue Jan 31, 2023 2:09 am

Replace all the ignition coils. Or use the new coil and swap between all the others. I have not found scanners accurate to diagnoses exact cylinder misfires. Still at that mileage I would replace all coils.

sw4nny · Post by **sw4nny** » Tue Jan 31, 2023 2:29 am

javis20 wrote: ↑Tue Jan 31, 2023 2:09 am Replace all the ignition coils. Or use the new coil and swap between all the others. I have not found scanners accurate to diagnoses exact cylinder misfires. Still at that mileage I would replace all coils.

To follow this advice up i would say replace all coils,if one goes the others are going to be going soon,
I have had coil failure in the past on more than one m54 engine i have replace all coils on all occasions and had not had a problem after doing so

Z4LauncherMan · Post by **Z4LauncherMan** » Tue Jan 31, 2023 2:43 am

Okay will do! I am ordering them now. Thanks so much for the advice!

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