My X' engine runs weird! Help needed!
 

Yesterday, When I was driving my X, suddenly the engine lost control. When I stopped it at red light, the engine run like someone pressed the gas paddle and released it and again and again, after I released brake, the car just speeded up and slowed down followed with the weird engine behavior, but I did not press the gas paddle at all.. The RPM of the engine just run to 2000 and backed to normal and then did it again and again after I changed shift gear from 'D' to 'N'. I pull it over and shut down the engine for 10 minutes, then start it again, the engine just did it again. No light up, no warning in the cluster, the engine did not die itself. What is the problem?

One year ago, I encountered the same problem, but difference is the engine died after several self-speed-up and self-speed-down and come with warning of 'engine failsafe prog' in the cluster. I had my car checked by dealer, and found that it was the throttle assy failure. But this time no warning, no light up, no engine dead, only self-speed-up and self-speed-down.

Any input is very much appreciated!!!

Check the articles to "re-zero" your throttle. It's something like, key in position 1 for 10 secs then off then back to 1 for 10 secs and again one more time. Then start.
http://home.comcast.net/~jns-johnson..._Procedure.pdf

Yup, either your throttle position sensor is going or you just need to recalibrate the throttle with the link in the above post.

is it something like this?
http://youtube.com/watch?v=BFmPPzHpa38

Yes, exactly like this.

Just saw the text, it's pretty interesting. But my x is 4.4i M62 engine, not M54 engine.

Maybe Cam sensor or Cam is going bad. Get those checked. Good Luck..

Finally, the problem was solved! It was the throttle housing assy failure. Dealer replaced it and everything backs to normal now. Since I replaced this part on 3rd May 2006 due to the same problem, this time dealer replaced the throttle under warranty (in HK, BMW dealer provides two year warranty for any part replaced by them), I just paid about US$100 for inspection.

One more thing, the dealer tried to fool me around by not mentioning this part was still under warranty and they tried to replace the MAF meter as well for me and charged me more than US$1,000 for the two parts including labor. They told me that they found fault codes of both throttle and MAF meter in DME, but I believed that only the throttle was failed, not MAF meter (I have experience on this proble before). Fortunately, I keep the repair invoice to show them that the throttle was replaced by them within 2 years and claimed warranty, also I refused to replace the MAF meter and ask them to re-install my old one back on, my x runs fine without any problem now. But I will buy a new MAF meter from outside dealer for only US$180 (bosch product) and replace it myself. Dealer charges more than US$640 for the part.

By the way, can anyone here tell me what will happen if the MAF meter starts to fail? Thanks!

MAF replacement big racket!
 

I was told 2 years ago by a good ind shop to replace MAF due
to code showing up. Did so, $425 for part and $85 to put it in.

Ran kinda rough again recently. While at breakfast I mentioned
this to some of my Jetski buddies. I told them this MAF looks like
two little wires and how could it fail?

They told me to got to auto parts store and get some MAF/carb
spray cleaner for $3. I took off air filter connection, sprayed liberally
with motor off.

You know the punch line.........car worked perfectly! Screw 'em when
they tell you to replace........!