M50 wont rev past 3500

[driftingminor913]

just got done swapping in my 94 M50tu into my 1990's 325i and im having a acceleration issue.

Keep in mind, the car doesnt have Cats, just a straight pipe all the way back. the check engine light is ON, i changed the fuel filter ( with no success) did a fuel pressure test (turn out okay) i notice that i had a coil that was sparking when the car was running so i swapped that out and also the long boot too... and it seem to fix the problem...till the next morning. it went back to misfiring and sputtering at 3k

im guna change the spark plugs cause i put some champions in them....

would that be the source of the problem since there just some "Ol spark plugs" ????

[RobertK]

Are you getting a CEL? If so have you attempted to pull the codes?

[ELIXIR]

check your injectors too... you may have a leaking injector leaking overnight causing the plug to foul.

[SkorcherX]

VSS signal?

[driftingminor913]

So this morning I got up n went to work in the M50 and this is what it was doing: (check engine light on the whole time) it wouldn't let go past 2500 then it would start to sputter/misfire. So later today I thought it would best to get the crappy plugs out, I went and bought some DENSO plantinums, put them in and now it's Better! Now it let's me rev to 4500k and will start to sputter after that.


After I put the plugs in me n a buddy hooked up the e36 diagnostic plug on a snap-op computer, we let the motor run and started to watch all the data information flow in. Throttle was on point, spark pulse was reading correctly, idle was between 800-1080, BUT the was a option on the screen called knock control..so we open it up and a graph was shown and every time we would rev the motor (neutral) there would be a spike on the knock control graph and as it idled down the spike was disappear?

My buddies conclusion was either I have a bad harness, bad knock sensors, or bad crank & cam sensors

[driftingminor913]

So today I put a different MAF on and swapped out the Cranshaft position sensors and went on a drive, now I can Rev all the way out to 7k but the problem is that there is NO power from 1000 to 3000

[Tico Frank]

Good Luck DOOD.

[driftingminor913]

So I'm confused on this now, I went to the JY and maybe thought I would be the whole harness and was guna pull on out of a E34 auto but instead grab a crank and cam sensor and the MAF, went home and put the MAF on and the crank position sensor on and gave it a whirl....THE CAR RAN like it was a bat out of hell n was fun! And then my check engine light came back on and it still ran fine, till this morning.

Gave my buddy a ride to work and as I was coming back home the car went back to not letting me go past 3500


Idk if it's cause it heated up or the DME relearned and found the problem

[driftingminor913]

I hooked it up to the scanner again today and the codes I got where: knock sensor circuit 1 &2, vehicle speed sensor, O2 which isn't hooked up at all.

And my speedo works so idk why it throws a VSS code, but I cleared them n drove it home and it ran fine all the way home. And halfway through the trip my check engine light came back on?

If anyone can post back some info that would be great!

[mentaleeill]

I hooked it up to the scanner again today and the codes I got where: knock sensor circuit 1 &2, vehicle speed sensor, O2 which isn't hooked up at all.

And my speedo works so idk why it throws a VSS code, but I cleared them n drove it home and it ran fine all the way home. And halfway through the trip my check engine light came back on?

If anyone can post back some info that would be great!

vss has nothing to do with the speedo working. the speedo is driven from the car harness and diff. the vss wire is at the c101 and x20, and needs to be hooked up.

definately replace the knock sensors as well. obd1 knock sensors are prone to failure and at 18 years old, i would say their time is up

no o2, means the car is running rich all the time, being in open loop. why not have one in there?