RPM dip on cold start

[bimmertt]

For the past few months, my 2014 xDrive35i has been having a rough cold start. Upon starting, the RPMs dip to the point where it sounds like the engine is about to stall, the RPMs then shoot up and stabilize. The car runs normally the rest of the day. I’m also getting a P0420 error code. I’ve tried replacing the o2 sensor and also cleaning the MAF and MAP sensors but this issue still remains. I’ve found other posts about this issue but there hasn’t been a clear resolution. Car has almost 90k miles. Has anyone resolved this issue?

[stocktree]

Possible vacuum leak?

[Hotflare]

Originally Posted by bimmertt

For the past few months, my 2014 xDrive35i has been having a rough cold start. Upon starting, the RPMs dip to the point where it sounds like the engine is about to stall, the RPMs then shoot up and stabilize. The car runs normally the rest of the day. I’m also getting a P0420 error code. I’ve tried replacing the o2 sensor and also cleaning the MAF and MAP sensors but this issue still remains. I’ve found other posts about this issue but there hasn’t been a clear resolution. Car has almost 90k miles. Has anyone resolved this issue?

I have the same issue too

[bimmertt]

To update this thread, since my original post, I’ve replaced the injectors, spark plugs, and the post cat o2 sensor. Issue still persists. However, the p0420 code is finally gone after I replaced the o2 sensor and I was able to pass emissions.

I did a little more digging and some people said having BMW update the software resolved the issue for them. That might be the next thing I try.

[TOPEC]

How old is ur battery? This happened to me recently as i havnt driven the car in about a weeks time, and is still on the original 2016 battery. First start stumbles n dip as well as revving high. Figured the battery is really low on charge so decided to put a charger on it when I got home. Next start about a week later no stumbling or dipping.

[tlow98]

Ok, so I had this issue too. There is also a very long thread in here with many other people having the same issue.

Some of us, including me, have solved it by doing the following.
- start with cold motor
- unplug the MAF
- start and run the engine through an entire warm/cold session. Drive it around. Don’t just idle it.
- wait until the engine is stone cold and plug the maf back in.

Mine hasn’t come back in maybe a year with this trick. I can’t explain it and it doesn’t make any logical sense to me but it worked and it was easy. Of course you’ll get a CEL with it unplugged but it will go away when you plug it back in.

I waited forever to try this bc it sounded ridiculous and then it worked and I was kicking myself.

Worth a shot.

Good luck!

[Bruce322]

I had the issue before. Bmw dealer did a diagnosis and updated DME/ECU firmware, only charged 1.5hours of labor and got resolved.

[stocktree]

Originally Posted by tlow98

Ok, so I had this issue too. There is also a very long thread in here with many other people having the same issue.

Some of us, including me, have solved it by doing the following.
- unplug the MAF
- start and run the engine through an entire warm/cold session. Drive it around. Don’t just idle it.
- wait until the engine is stone cold and plug the maf back in.

Mine hasn’t come back in maybe a year with this trick. I can’t explain it and it doesn’t make any logical sense to me but it worked and it was easy. Of course you’ll get a CEL with it unplugged but it will go away when you plug it back in.

I waited forever to try this bc it sounded ridiculous and then it worked and I was kicking myself.

Worth a shot.

Good luck!

Sorta makes sense. When you first start a car, the computer is in open loop, where the car ignores certain sensors. Then after a few seconds, car goes into closed loop and looks at all sensors for feedback. Unplugging the maf may do a reset of values or something.

[dyezak]

Logs?