[lcasale]

I've been encountering a strange problem on my 2008 335xi that's happening more and more often lately. My car will occasionally start with a pretty rough idle, but after driving off the rough idle goes away, but the car ends up in limp mode without throwing any codes or warning lights.

Punching the gas during this time makes the RPM's slowly climb with barely any acceleration (pretty sure a prius can pass me if it wanted to). Then when the gears shift the car jerks a little bit, like it wants to unleash power but can't, before going back to a very slow acceleration. If this happens on my way to work I usually restart the car at a light and everything goes back to the way it should (100% success rate).

I just replaced all the spark plugs and 1 coil ~5k miles ago. I'm running map 1 with the latest firmware as of today (28_3). This used to happen maybe once or twice a month over the summer, but as the temperature has dropped I'm finding it happening 2-3 times a week. Any ideas on what the root cause may be or where I can start investigating?

[CarAbuser]

Sounds like HPFP.

I had those exact symptoms before getting mine replaced. Rough idle then as soon as I'd go to pull away a CEL would spring up.

Only happened occasionally too.

[lcasale]

Damn!!

I forgot to mention I brought my car to the dealer at the beginning of the summer (without the JB4) to fix the rough idle. They ended up walnut shell blasting but said the HPFP was fine. After that my idle was silky smooth but has been progressively getting worse. Now that this is happening so often I'll try riding without the JB4 and see if I can replicate it.

The strange thing is, I'm not getting the CEL at all. Thanks for the tip.

[Z&M Auto]

Originally Posted by snizzles

Damn!!

I forgot to mention I brought my car to the dealer at the beginning of the summer (without the JB4) to fix the rough idle. They ended up walnut shell blasting but said the HPFP was fine. After that my idle was silky smooth but has been progressively getting worse. Now that this is happening so often I'll try riding without the JB4 and see if I can replicate it.

The strange thing is, I'm not getting the CEL at all. Thanks for the tip.

Try to do a log. Been chasing this one too just way to busy to finally get around to diagnosing it. Problem went away after all injectors were done. Came back a few days later. No CEL or limp, restart usually corrects it. Sometimes two restarts. Stalled three times after a cold start. If it sits for more than 6-8 hours same issue. Sometimes I can go 2 weeks without it happening on a cold start. All signs point to a fuel issue. Keep me updated.

[lcasale]

I haven't been able to log it yet, but it acted up the worst I've every seen so far riding on the highway this weekend. It was enough to trigger the CEL, limp mode and the codes below. I have a service appointment in two weeks and I'm going to be traveling before then so I ended up taking the chip out today.

I'm really hoping in the time between I can get it to act up again without the JB4 installed before my service appointment.

Edit: @Z&M Auto - That's EXACTLY what I'm experiencing. Sometimes one restart does it, sometimes two are needed. Sometimes it can go a month without issues, other times I have the issue 2-3 times a week for a couple weeks. It only happens with the JB4 is installed and never around the time it finally makes its way to the dealership.

[lcasale]

Alright so I was easily able to get the car into limp mode this morning without the JB4 installed. Once it goes into limp mode I also get a pretty rough idle. So whichever part that was starting to fail is finally reaching its end. It goes to BMW next week so I'll post an update when I hear back.

[Seven11]

Injectors?

[lcasale]

Alright so the culprits are the HPFP and LPFP Sensor and they're both getting replaced. I can't wait to get my car back