FIXED: Stuttering at 3k RPM.. has anyone figured this out? --- VIDEO INSIDE

[JUNGLISTluder]

I plan on pulling the engine, sealing it up a bit better, replacing whatever the fuck I see, and dropping it back in with a lighter flywheel.

I feel you Jake.. I have spent a lot of time and money making this thing *like new* and this is the worst symptom it could possibly have. A 3500 rev limiter on a fucking high-winding 4-cyl is terrible!

Gotta stay motivated and get this shit done soon!

I had all the exact same symptoms as you. 3500rpm limit when warm and 1244 code. A new crank sensor fixed it. My old one even tested within spec. I don't see that you replaced this sensor, so I would really start with that.

[Nairb]

Thanks Jung, will do!

[snitzer]

Nairb,

does your m42 have the adapter harness in place?

[Nairb]

Nairb,

does your m42 have the adapter harness in place?

Wat? :|

[snitzer]

where the wiring harness screws into the back of the afm there is a (maybe) foot long chunk of wiring harness that was a recall or tsb addition to fix some sort of idle problem. mine had it, I didn't know what it was and removed it. my car ran fine without it for a couple years. now that i'm having problems i can't find my old one too put back in.... was wondering if your car has it.... if not, it might be something to try. if it does have it...then never mind...

[Nairb]

where the wiring harness screws into the back of the afm there is a (maybe) foot long chunk of wiring harness that was a recall or tsb addition to fix some sort of idle problem. mine had it, I didn't know what it was and removed it. my car ran fine without it for a couple years. now that i'm having problems i can't find my old one too put back in.... was wondering if your car has it.... if not, it might be something to try. if it does have it...then never mind...

Thanks for the info, but I don't think I have that. Here's a pic of my bay:

[snitzer]

the connector under your k&n sticker.... if you follow it back about a foot and there is another connector...that's the extension piece.... the tsb might have been serial number specific.... if you don't have the part, maybe there is someone near you that does and you can give it a try and see if it helps.... i'm barking up trees here...and trying to find one locally but have yet to find it.

[Nairb]

Replaced my crankshaft position sensor!



And now the car won't start. Turns over, feels and sounds like it's going to start up, and then just keeps cranking. What next?

[mr ilia]

Put the old back in, see if it starts.

[snitzer]

bttt

any news?

[snitzer]

mine is fixed..... number 2 spark plug wire had a small piece of material missing at the bottom of the plug end of the assembly, you could see the corona trail clearly once i rolled it over an actually looked at it.
I took a dab of RTV blue, filled the missing area and viola, runs like a champ (with 250,000 miles anyway)... yep feeling pretty stupid ... however... always look at the plug end...lesson learned.

[TobyB]

Does the M42 ECU look at the wheel speed sensor? 5k is the point that the M20 limits
if it doesn't detect any wheelspeed- I guess to prevent the 'brick on the accelerator engine blow'
thing they do with aircooled VW's.
Long shot, but if it's losing wheelspeed, maybe that's what's doing it.

t

[Nairb]

Whoops, did not realize this thread had received any responses.

Finally said fuck it and took the car into my mechanic today.

So far we have confirmed, fuel, spark and compression (210,220,185,210) in the engine. The car will crank, but still misfire and not start. Pulled 0 mile plugs and they were flooded and carbon buildup was ridiculous.

Hopefully we can diagnose this quickly, this is really making me lose my interest in my e30 and it sucks.

[gt88]

Possibilities

Ok, read through all the story here. Got a suggestion:
Have your professional mechanic check cam and crank waveforms. A couple things to look for:

1) Timing. Your DME trigger wheel is rubber mounted, and most likely slipped. This can be verified by watching the cam and crank position sensors' waveforms, and both must match. Your DME (harmonic balancer) is the primary timing reference for the DME, and is fine tuned/verified by the cam sensor input. I recently ran into 4 consecutive used DME wheels with completely different timing, and could change timing from retarded, to ~ok, to way advanced by simply swapping wheels.

2)Amplitude. The BMW DME is very sensitive to the crank sensor's amplitude. Ran into a Bosch replacement ckp sensor with 1/3 the amplitude of a factory sensor, caused the car to go into a form of "rev limiting". I dont have the timebase values with me, but I can post them if needed.
You can check for this by watching the timing with a timing light, and monitoring the injectors- when it "rev limits", you will see at least 1 pair of injectors being shut down by the DME, and see @ a 10 degree ignition retard.

Another fun fact about amplitude, is that it is affected by spacing between the sensor tip and the DME wheel. Check gap at your DME wheel and ckp sensor, I would bet you would also see a sizeable gap difference depending on position. On a scope, you can see this varying gap as almost a helix style pattern at the crank signal.

If your car is consistantly cutting out at roughly the same rpm, just check the timing with a timing light, see if your timing is being retarded when this happens. If you have the ability, see if at least one pair of injectors is cutting out at the misfire event, as well.

If all the above is relevant, a new factory DME wheel is over $800. FUN.

Any aftermarket wheels out there?

Good luck

[Nairb]

FIXED. Read here.

Well, looks like my crankshaft sensor was bad. The sensor I replaced it with was defective and caused the car not to start at all. New crank sensor, new plugs and now the car is back to it's normal state! Finally, I have my car back!

Still needs a nice wash, and unfortunately I sold my BBS's so it's on weaves for now, but I'm so happy it's running well again.

It was the crankshaft sensor!