No hesitation after resetting DME, WHY?

[mdistel]

I'm trying to troubleshoot my poor running 95 M50. If I reset the DME by disconnecting the battery the car runs great during the initial learning stage. After that it begins to hesitate like crazy.

My question is what is different during the initial learning stage? Does the car run richer? Does it ignore the input from the O2? Does it ignore other sensors? This would help me narrow my problem down as it should rule out parts like the fuel pump, cat, muffler etc..

Thanks

Mark

[Wayne 962]

Is it pulling any codes?

-Wayne

[mdistel]

Yes and no. Sometimes I get a lambda and knock sensor 1 other times I get nothing. Brett Anderson ran a real code scan using BWM tools and found it had a out of spec MAF at 3750 RPM. I found that my intake manifold is cracked so I'm replacing it and some other parts and hoping that does the trick.

Mark

[Wayne 962]

Cool. A vacuum leak from the manifold would cause all sorts of problems. Knock and lamba together also indicate very bad gas...

-Wayne

[cmelton]

I have 94 325iC that had exactly the same symptoms. Lambada code intermittingly. Usually ran great for 10 minutes then it turned evil. When it did this I pulled over and removed the O2 sensor relay and it ran decent.
BMW wanted $138 for 1 O2 sensor, local auto parts wanted $93, I read a forum where the 2.5 liter 6 cylinder used the same sensor (3 wire heated) as a 87 mustang 5.0 but had a different plug. All made by Bosch by the way. I bought the Mustang sensor for $38, cut the plug off my old sensor and it has been running like a champ for 7 or 8 months now.

Hope this helps
cmelton