To the gurus among us...

[mooserilius]

Let me give you some back story.

I bought a 1992 318i sedan (e36 of course). A couple months later I'm coming down the highway, downshift to pass some old guy and tach it up... Kabloomaloomaloomloom!! She's dead. Valves embedded in pistons kind of dead.

Anyway, Long story short... I find another M42 from a 1992 sedan, exactly the same, that runs and I freshen it up with new gaskets, water pump, thermostat, etc. (No internals were replaced). Throw it in the car and have replaced the fuel pump and filter as well.

Here's what the car is doing now that it has been swapped. I can crank it up and let it run. It will idle properly and run very smoothly. I have let it idle as long as about an hour. Then I can go out and start driving it. It will run smoothly for about 3-5 min/2-3 miles. And out of nowhere it will just lose power and and die out. Once it does that it does not crank back up right away but will turn over. After a min or two... or five, I can get it to run but it will run rough. At this point it sounds as if it is missing or bad injectors and of course trembles and shakes. Then as it is running for a min or two, it will begin to idle smoothly and run fine for another mile or two and it will do the exact same thing. This is as far as I can get it, because at that point I turn around and pull it back into the garage.

My thoughts so far have been FPR or MAF. Now, I even unplugged the MAF and let it run without it, then hooked it back up. With it unplugged it idled funny, then hooked up, it idles like its supposed to. I'm not ruling that out but just trying to give the entire scope. Also I pulled the line to the FPR and it doesn't have any fuel in it. I'm aware that it could be just stuck or something too, but this is all I've got so far. Lastly I've checked for vacuum leaks and there doesn't appear to be any.

I also have not done a Fuel Pressure test on it yet but as stated, it will idle and rev at home for an hour and then even drive for a short distance perfectly.

Please let me know your thoughts. Any help is much appreciated.

[1998ccc]

Check O2 and DME coolant temp sensor and report back.

[sherbert22]

I've been away from the m42 for awhile, but that sounds like a crank position sensor symptom to me. You can try to cool the sensor off when it happens and see if it smooths out again. That's usually how to tell when they fail.