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

[Nairb]

Ok, I've searched all three great e30 forums (r3v, e30tech, m42club) and I have tried everything from those threads. They are usually ancient, and nothing ever seems to be resolved about this problem.. so here it is:

M42 stutters when it hits 5k RPM. It acts just as though I am hitting the rev limiter.. except I lose power and my tach jumps.. it will keep doing this until my car starts dropping in RPM. I am completely stumped.

Here is a link to a video that I've made: http://www.youtube.com/watch?v=bPNIZQ5kn3w

Here is a pretty complete and up-to-date list of what I have done to the car that would affect engine performance:

Mods:
Mark D 93 Octane Chip
K&N Air Filter

Maintenance:
New Throttle Cable (149,000 - June 2011)
New Camshaft Position Sensor (149,000 - June, 2011)
New Bosch O2 Sensor (February 2011)
New Fuel Filter (July 2010)
New Timing Chain Tensioner (March 2010)
New 4-Pintle Bosch Fuel Injectors [Part #:0 280 155 710] (September 2010)
New OEM Bosch Spark Plugs (September 2010)
New HQ Autosport Coil On Plug Kit (September 2010)
Fixed the "Mess Under The Intake" (September 2010)

I am running 93 Octane fuel.. always have. No hoses are getting crushed and everything is hooked up properly. Still have not replaced fuel pump, but I don't see why that should be a problem.. never have had a problem with fuel pressure.

Anyone? Ideas? HALP!

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FIXED. Read here.

It was the crankshaft sensor!
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[mr ilia]

You need new AFM. This exactly what I had, except with me it was happening at about 6000 rpm, like a rev limiter. The engine light would come up briefly when hitting the "limiter".

[Dj Buttchug]

is your spark plug gap correct?

[Balleristic31]

I was gunna say afm as well. I have one if u need it.

[Nairb]

is your spark plug gap correct?

Thanks for the responses guys.

Buttchug, I just replaced the plugs with OEM Bosch about.. 5000 miles ago? Used factory torque specs on the plugs.

[Dj Buttchug]

Used factory torque specs on the plugs.

you mean factory gap?

if this was my car heres what I would do. Pin out every sensor crank sensor and cam sensor. ect ect ect.

Im leaning towards its most likely electrical. when the engine hits the right harmonic vibration around 5k its causing something to loose signal.

[immajackuup]

op what cat-back you have?? sound pretty nice.

[Ryann]

OP, you might be able to fix your AFM using the information in this video:

http://www.youtube.com/watch?v=-11J8XawQtc

I did.

[Dj Buttchug]

good video

[Nairb]

OP, you might be able to fix your AFM using the information in this video:

http://www.youtube.com/watch?v=-11J8XawQtc

I did.

Awesome.. I will definitely try that first!

[Nairb]

Thanks for all the responses guys.

Ok so, tested the car today at low temperatures... the car revved perfectly and no hesitations at all throughout the range! So, it seems as though it is only doing it when the car is warmed up. I redlined (7,000 RPM) it probably 6-7 times at low temp just to make sure.. and also performed different throttle positions.. the car acted as it should..

So what's that mean?!

[Ryann]

Are you getting a CEL during the funk? If not I'd guess your A/F is good enough during warm-up to hide the symptom, but not good enough once Motronic enters closed loop mode. Does it start hard when warm?

[Nairb]

Doesn't really start hard when initially starting.. probably revs to like 2k and then falls.. no CEL at all and no codes thrown during a stomp test.

IMMAJACKUP.. no idea what exhaust setup it is.. PO put it on.

[Ryann]

Watched the video again, very weird. Like you said it sounds JUST like the rev limiter from the exhaust. Have you tried swapping DME's? If you'd like to I can mail you my good spare to try out.

[Nairb]

I have not tried swapping DME's.. but I'm willing to try anything.