[OGM1]

My N52 has been having some misfire issues. It was throwing a code for cylinder 1 misfire. Would throw visual drivetrain error that would self clear. Misfire was pretty bad with loss of power.

Plugs didn't look bad but I changed them anyways. That appeared to have solved the problem as far as throwing a code. However, there is still the occasional stutter at idle. There is no loss of power and car runs fine.

My next step is coils, but I don't want to throw parts at this thing without knowing. I use bimmerLink to clear and read codes. As of now I do not see anything new. I would like to see fuel trims to rule out a leaky injector, but that option isn't available in the bimmercode app. I do see a couple informational codes for "data gear train missing", "request torque crankshaft gearbox", and"request torque crankshaft gearbox 2".

Any ideas on what to check next? Engine is N52B30 variant from 2012. 145,000 miles

[OGM1]

Update. No new codes for misfire. However, I did get a 118602 error. Lambda probe in front of cat, fine tuning of the mixture: exhaust gas after cat too lean

[OGM1]

new o2 sensors on upstream side. Don't like throwing parts but they do have 145K on them. Reset light. No new codes after 50 miles. MPG seems worse though.

[Mixzzz]

Originally Posted by OGM1

new o2 sensors on upstream side. Don't like throwing parts but they do have 145K on them. Reset light. No new codes after 50 miles. MPG seems worse though.

You should replace also downstream o2 sensors. On N52 they are used to trim(calibrate) the upstream o2 sensors so if theyre not working correctly, neither will upstream ones and youll wont have precise air/fuel ratio. You could end up killing cats... You can buy universal bosch ones which you need to splice in to the existing connect or just get the correct ones.

Which brand upstream ones you got?

[OGM1]

I used the Bosch direct fit. Part number 17230 and 17231. Pretty much identical to the oem ones

[bogdan18493134]

Originally Posted by Mixzzz

You should replace also downstream o2 sensors. On N52 they are used to trim(calibrate) the upstream o2 sensors so if theyre not working correctly, neither will upstream ones and youll wont have precise air/fuel ratio. You could end up killing cats... You can buy universal bosch ones which you need to splice in to the existing connect or just get the correct ones.

Which brand upstream ones you got?

From where did you find that information about the downstream o2 sensors? As far as I know they only monitor the exhaust

[OGM1]

Replaced lower sensors. Fuel eco still bad. Probably down 3-4 mpg. No lights returning though. MPG gauge acting very odd. Will randomly drop as the car downshifts under zero throttle. Definitely reading lower than it used to while cruising 25-45 mph zones.