M50 no power

[Sharino]

Swapped a M50NV into a friends car, ran great for a few months but just the last few weeks, it starts to have no power at all when running, Was pretty intermittent, now it is getting more and more common. You driving down the street and its like the car has no power all of a sudden, rev it a little and it starts to go again. Can act like that for the entire drive or sometimes its works perfect for 10 minutes straight. This happens when car is cold or hot. o2 sensor is currently disconnected, never ended up installing one but it use to run fine that way.

This is what I trying swapping today with a collection of used parts I have:
-fuel pump
-cam position sensor
-fuel pump relays
-maf
-new fuel filter

-tested all coils resistance, all where between 1.4 and 1.5 ohms
-tested power at the fuel pump, constant voltage while driving

Any ideas what else I can check?

[scottinAZ]

Had similar issues with my vanos motor. If its pre87, check the lift pump in the tank. Check the cps as well

[Sharino]

Its a 90, I thought they only had a single fuel pump, the one in tank, that is the one I changed.

CPS, is that the crank sensor? Is there an easy way to test it, especially if its intermittent?

[e30shmobberr]

maybe this?

http://www.r3vlimited.com/board/showthread.php?t=192533

[scottinAZ]

Its a 90, I thought they only had a single fuel pump, the one in tank, that is the one I changed.

CPS, is that the crank sensor? Is there an easy way to test it, especially if its intermittent?

you only have one pump. Mine was a combination of the in tank lift pump (that you dont have) and the knock sensors (that you also dont have).

IIRC the bentley has the specs on the crank sensor. One other avenue is to have the codes actually scanned with the proper tool. the stomp codes really dont tell you shit (mine did not tell me the knock sensors were fucked). armed with a good scan, you can more readily troubleshoot without just throwing parts at the car.

[Sharino]

I tried reading codes, I have both Carsoft and INPA, could not pull anything, keeps saying module not responding, yet my setup works fine in other cars.

Its a really strange issue, all of a sudden, no power, doesn't stall or make any noises, just like the throttle stops working for a few seconds.

I have tons of E30 and M50 parts kicking around so upto this point it wasn't a big deal just swapping parts in, but I am really stumped.

[scottinAZ]

check your wiring. Something is off if you cannot connect to the reader system. May be the root cause of the problem.

[nando]

I doubt you'd get much out of INPA with the M50NV ecu anyway - it's basically the same thing as Motronic 1.3 with more injector challens and ignition drivers.

have you checked fuel pressure? leakdown/compression?

also whenever I read a diagnostics thread and somebody says "I left XY sensor out and it seemed fine before" I just stop right there. The motor was meant to run with that sensor, the first place to start is to make sure they're all connected and working properly to begin with.