[E90 ME]

Okay... so lately my car has been acting very weird during cold starts, it would have a very rough start, no long cranks both HPFP and LPFP have been replaced.
No codes pop up, so I have no clue what to replace. Doesn't idle wierd, drives perfectly normal. Went to the dealer (CPO) and they couldn't duplicate the problem. The car is FBO and JB4 G4.
Car has a little over 51k.
Any input would be appreciated.

[patrick335i]

Have you ever done a walnut shell blast to your intake valves? Probably have a shit load of carbon buildup causing the rough idle. If you have no misfires/codes being thrown, I would say it's probably carbon build up. 335i's tend to idle a bit rough though but mine has gotten better since replacing my injectors and spark plugs.

[E90 ME]

Originally Posted by patrick335i

Have you ever done a walnut shell blast to your intake valves? Probably have a shit load of carbon buildup causing the rough idle. If you have no misfires/codes being thrown, I would say it's probably carbon build up. 335i's tend to idle a bit rough though but mine has gotten better since replacing my injectors and spark plugs.

Yes I have already done the walnut blasting at 49k. That still didn't fix the problem.

[kctim]

Did this start happening right after you went catless?

[JStang]

I have the same problem.

[E90 ME]

Originally Posted by kctim

Did this start happening right after you went catless?

No not really at first the symptoms were long cranks, but not all the time. Then the cranks would be very rough, it's like that car is struggling to start up. Keep in mind that the car drives perfectly normal even with the tune on, at WOT no misfires/limp modes or CEL.

[Jklad]

Sounds like my issue also - I've been lazy about correcting it with the cold weather, but from what I've gathered it could be:
-leaky injector
-low pressure fuel sensor (my next step - have you replaced yours recently?)
-either of the fuel pumps

[E90 ME]

Originally Posted by Jklad

Sounds like my issue also - I've been lazy about correcting it with the cold weather, but from what I've gathered it could be:
-leaky injector
-low pressure fuel sensor (my next step - have you replaced yours recently?)
-either of the fuel pumps

The HPFP was replaced at 10k, LPFP was replaced at 34k along with injectors.
Recently the only maintenance that has been done to the car was water pump, oil filter housing gasket, and walnut blasting.
The one thing I have also noticed is that, when I'm unlocking the car I can hear the fuel pump prime most of the time. Sometimes I can't even hear it before a cold start.
I will try to post a video as soon as I get off work.

[MAC335i]

I dont know if this will solve your problem because it sounds different than mine. You say the car has a "rough crank"? As in when the starter is turning the motor? Once it fires, it idles fine?

My problem was a very rough cold start. What I mean by that is the car was misfiring while idling during the cold start (when the idle goes to ~1k rpm and then slowly comes down to normal after about a minute or two). You could hear it missing and feel a little shake every time. It smelled like raw fuel too.

The problem: O2 sensor was loose! Im assuming it was not torqued down properly during install and came loose over time due to vibrations.

So some air was probably getting in the exhaust and the O2 sensor was thinking the car was lean and needed to give it more fuel, causing it to run extremely rich during cold start (cold start naturally runs the car a little rich for that 1 or 2 minutes so this made it even more rich).

I also got crazy loud backfires during a shift after going WOT. Once the O2 sensor was torqued to spec, the problem was solved.

[E90 ME]

Originally Posted by MAC335i

I dont know if this will solve your problem because it sounds different than mine. You say the car has a "rough crank"? As in when the starter is turning the motor? Once it fires, it idles fine?

My problem was a very rough cold start. What I mean by that is the car was misfiring while idling during the cold start (when the idle goes to ~1k rpm and then slowly comes down to normal after about a minute or two). You could hear it missing and feel a little shake every time. It smelled like raw fuel too.

The problem: O2 sensor was loose! Im assuming it was not torqued down properly during install and came loose over time due to vibrations.

So some air was probably getting in the exhaust and the O2 sensor was thinking the car was lean and needed to give it more fuel, causing it to run extremely rich during cold start (cold start naturally runs the car a little rich for that 1 or 2 minutes so this made it even more rich).

I also got crazy loud backfires during a shift after going WOT. Once the O2 sensor was torqued to spec, the problem was solved.

Yes, when the starter is turning the motor it is very rough, like it barely wants to start. Once the motor turns over everything is normal, idles smoothly nothing out of the ordinary.
But I will check out my O2 sensors and see if they are loose.

[Jklad]

Originally Posted by MAC335i

I dont know if this will solve your problem because it sounds different than mine. You say the car has a "rough crank"? As in when the starter is turning the motor? Once it fires, it idles fine?

My problem was a very rough cold start. What I mean by that is the car was misfiring while idling during the cold start (when the idle goes to ~1k rpm and then slowly comes down to normal after about a minute or two). You could hear it missing and feel a little shake every time. It smelled like raw fuel too.

The problem: O2 sensor was loose! Im assuming it was not torqued down properly during install and came loose over time due to vibrations.

So some air was probably getting in the exhaust and the O2 sensor was thinking the car was lean and needed to give it more fuel, causing it to run extremely rich during cold start (cold start naturally runs the car a little rich for that 1 or 2 minutes so this made it even more rich).

I also got crazy loud backfires during a shift after going WOT. Once the O2 sensor was torqued to spec, the problem was solved.

Wow, how did you determine the o2 sensor was loose? Was it a primary or secondary o2?

[Miller335]

I'm at 29K miles have the same issue after getting a misfire in #5.

I replaced the plugs with NGK's gapped to .22, no more mis-fires car runs awesome other than it idles rough on first cold start of the day for about 30 seconds.

I gapped to .25, still same issue.

I then reset adaptions, ran only pump gas and now the first cold start isn't nearly as bad but it's still slightly there but again it greatly improved.

If I cannot figure this out I will have to remove JB4 and have it diagnosed at a dealership cause I'm ready to go FBO but I need to get this resolved first.

[E90 ME]

Just little update, jacked up the car last night and check at all my O2 sensors and post cat O2 was loose.
Started the car up this morning and all is well, car starts up perfectly (no rough cranks). I will keep you guys updated if the rough cranks occurs back again, but hopefully it is fixed.