3000 rpm R3v limiter?

[Lurker27]

I have a 325is, and i just had to redo the pump pump wiring (positive signal from the relay must have gotten corroded/shorted out).

I went to go flog the car a bit to charge the alternator, and it will NOT go above 3000 rpm in drive. It sounds like it is bouncing off a limiter. Throttle position doesn't matter, it just happens at 3k rpm. If I have in park (autotragic) it will rev to 4500 or so before it seems to stumble and die more naturally.

Motronic 1.1 stomp test throws no faults.

I think this is O2 sensor or sensor heater related - thoughts?

[backtrail69]

sounds like fuel starvation. When is the last time you changed the fuel filter? And have you tested fuel pressure yet? Many machine shops can test your injectors as well if you are worried they are clogged.

[Lurker27]

I have not tested fuel pressure, but thanks for that suggestion - I was just SURE it was electric - the limit seems solely rpm dependent.

[backtrail69]

Test your Reference sensor on the front of the engine per the bently ohm test and check for any bad wiring especially under the intake manifold. The last step would be to try a different ecu, you can usually get them pretty reasonably priced off the forum.

[deansbimmer]

I had this happen to me; consistent rev limiter, no faults, etc. I found that I had bad gas. Really. Half of what was in the tank was water. Water goes to the bottom, open the drain and see what comes out.

[Lurker27]

Disconnecting O2 didn't solve it - I also put half a can of seafoam in the tank (~2gallons of gas), ran it for a while and did the intake seafoam, then topped off with dry gas. No change there either. I'm thinking ECU, AFM, or TPS at this point...or possibly the wiring...my odometer recently stopped working, and then my fuel pump wiring went bad...I didn't connect those 2 problems until today.