Intermittent 4x4 light, Stumble on Acceleration, but no Codes (after VCG change)

[CW in PB]

2008 X3 3.0, around 118K miles. No mods.

Some background: Had the transfer case actuator triad (4x4, Brake, ABS) about six months ago. Did the "budget" repair of rotating the plastic cog such that the worm gear had a fresh set of teeth to engage with. This cleared the lights and I hadn't had any issues....until now.

After putting off a seeping VCG I decided I had to get it done when we could actually smell the burning oil in the cabin. Got the parts, read the DIYs, watched Youtube and got on it. After I got it all back together, lean codes appeared about 2 days later, but car ran fine even during a Las Vegas to San Diego trip (I had to get back as my daughter was starting school). The next day after a doctor's appointment, car started to hesitate/stumble upon initial acceleration and only the 4x4 light flicked on and off. I was able to get home, but no codes popped and no SES. Decided to reinspect my valve cover job and upon doing so, saw that I missed a huge crack/failure in the valvetronic gasket. This explained the oil pooling in that middle valve cover bolt hole. Got a new gasket, carefully installed the motor back in using the hex key to "reel it in" and did the key-to-second position relearn procedure a few times. Started up great, nice idle, and no more lean codes (no codes at all).

But that stumble/hesitation and flickering 4x4 light problem came back after about 5 miles.

I'm hoping that my VCG change didn't cause the stumbling (although I know it's possible/probable?). I've ordered one of the replacement carbon fiber reinforced cogs for the transfer case actuator to see if maybe that will solve the problem (at $10 probably a worthwhile investment anyway). I should have that in today or tomorrow.

Any other suggestions if this doesn't work? Could it be a mucked up eccentric shaft sensor (please say no)? Something else entirely?

Can I safely unplug either the valvetronic motor or eccentric shaft sensor as a trouble shooting step? If the stumbling continues, would this direct me back to the transfer case as the culprit?

Thank you.

[jclausen]

If the valvetronic sensor was acting up there would be most likely faults stored for it and if there is oil in the connector that could condem it too. I don't think the car would drive right at all with the sensor unplugged, check for faults. Electronically since ther are so many systems tied together I would check faults first

[CW in PB]

Thanks, Jbird. I'm going to go for another drive and see if any faults register. I'm hesitant only because I don't want to cata$trophically damage something while troubleshooting.

[CW in PB]

Started up and drove around for a while. This time, got a lot more herky jerky hesitation upon initial acceleration from stop...but no 4 x 4 lights and no codes on my Creator scanner. Stopped and got gas, started and then no issues. On the way home, called local indy shop who said come on in and we'll take a look. Whole way up (mostly highway, and again no issues). They looked with their whiz-bang scanner and it showed no codes related to valvetronic, ESS, or even transfer case (did have a 2EF7, T-stat Activation code which I'll tackle soon). They suggested that due to the recent maintenance including valvetronic removal, perhaps the computer had to "relearn" and basically right itself. Whole drive home, no problems. I'm going to change the transfer case actuator gear nonetheless. Assuming the problem doesn't come back, I'll assume it was a ghost in the machine or glitch in the matrix.

[bmwdirtracer]

For future reference, there's really no need at all for the valvetronic "relearn". You bolt it in, and drive. Yes, I know, that's what the directions say : SOMETIMES. In reality, pros don't waste the time.

I suspect that you have a major intake system leak, or your MAF isn't plugged in. Alternatively, as jclausen indicates, if that valvetronic sensor plug has oil in it, this can cause your issues....and also ruin your wiring harness and DME. (There is a service bulletin on this)

[CW in PB]

Wouldn't I have some lean, mixture adaptation, or MAF codes? I did have bank1 and bank2 lean codes before I replaced the valvetronic gasket (it was wrecked) but they're now gone and haven't come back, at least not today. I inspected the ESS plug and didn't see any oil. Still, I think I'm going to replace that seal (without taking the VC off) as a bit of insurance.

[bmwdirtracer]

Oil in the plug doesn't happen because of a bad seal, it comes through the sensor. Then It travels up the wiring harness to the DME. And I really don't think you can replace that seal with the valvecover on, though I've never tried.

[CW in PB]

Check this out: https://www.newtis.info/tisv2/a/en/e...lid/1VnYDt5VKK Dunno about the special tool needed, think I've read other threads where care and patience when reinstalling is the key...

[bmwdirtracer]

Okay, I guess it can be done; as I said, I never tried. I always change this seal when doing the VCG. However, the seal is not what causes oil to leak through the sensor, and pump up the wiring harness to the DME.

Since it seems that you don't have codes now, you might want to wait for more clues?

[CW in PB]

So far, no clues and I'm ok with that. Running great with no seeping/leaking. More importantly no lurching starts/codes. Thank you.