Help! M42 running poorly or not at all!

[porsche gt1]

I still think it is a fuel delivery issue. Did you check for a fuel leak? how about a plugged filter? Maybe your pump is on it's way out.

[dirty30]

I had this same thing happen to a freind of mines M42. It seemed to get worse every week. I had had enough so finally I pulled the intake manifold and found a peice of the lower intake manifold gasket had been screwed up on the number one cylinder. This caused un-metered air to be sent into the combustion chamber. The result was the O2 sensor was sensing a lean situation, so it enriched the fuel mixture, which fouled the plugs, caused a misfire, ruined the O2 sensor and finally threw a check engine light. All this was caused by a simple vacuum leak. The situation you are experiencing is the Motronic trying to "hide" the problem.... I would start with the basics before jumping to conclusions on the big stuff.

[dude8383]

I had this same thing happen to a freind of mines M42. It seemed to get worse every week. I had had enough so finally I pulled the intake manifold and found a peice of the lower intake manifold gasket had been screwed up on the number one cylinder. This caused un-metered air to be sent into the combustion chamber. The result was the O2 sensor was sensing a lean situation, so it enriched the fuel mixture, which fouled the plugs, caused a misfire, ruined the O2 sensor and finally threw a check engine light. All this was caused by a simple vacuum leak. The situation you are experiencing is the Motronic trying to "hide" the problem.... I would start with the basics before jumping to conclusions on the big stuff.

good point...ill look into this tonight!

[MikesJo]

Bad coil pack? I had two bad coil packs and the car was stuttering a bit.

[glucklich21]

Sorry for this bump, but what was the conclusion of the problem?

Mine was running perfectly the previous day. Then yesterday it started running like OP's when I went to start it for the first time.

[Matt-B]

check afm and shit man.


afm is my worst fucking enemy

[trackjunkie21]

I'm about 90% sure it's a vacuum related problem. Spray the vacuum lines with some starter fluid, see if the idle jumps. When you start the car when it's cold, does it surge? Does the idle fluctuate a bit? If so, this may be a faulty 02 sensor. BMW 02 sensors are maintenance items, replace them every 10 years or so.

[dude8383]

It was a faulty ECU, replacing it solved the problem!

[glucklich21]

Well fack.

[gearheadE30]

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