m50tu bad hesitation, loss of power, rev limit around 5.5k

[pmat]

My m50tu has been pretty low on power for the last few months, not bad but it didnt run like it used to. Then about a week ago i gassed on it and it started sputtering around 3k. Now it sputters around 3k, kicks back in kindof for a little, then hits what seems like a revlimiter at around 5.5k. It only does it when hot, when its cold it runs great but is still a little low on power. Throws code 1221 (o2). Have tried a working o2, fpr, cam posistion sensor, tps. have 1 known good spare coil and moved it thru all 6, no change. Fuel pump is about a month old so pressure shouldent be a problem but it was an airtex :(. Compression is good, cat not clogged. I am stumped and almost a week of googling has gotten me nowhere. Any input is appreciated as i am stumped
a video:

[franky2fingaz]

Have you checked the exhaust manifold for leaks? Sounds a little 'raspy' from Video.
You absolutely sure that spare sensors are good?
Did you test the wiring to the O2, MAF and all that apply?
Is VANOS making noise?
How's the fuel pressure from the pump?

[ascendotuum]

Sounds similar to what mine is currently doing. My problem is the vanos - verified by disconnecting the vanos solenoid and the problem went away. You could try this

[NickL]

Vanos seals.

[franky2fingaz]

http://www.youtube.com/watch?v=JPlKrOC718w

in case you're itching to get fingers dirty

[pmat]

I'll unplug the solenoid and take it for a spin i guess, wasnt thinking it could be the vanos, its quiet and until it started running bad i could even feel it kick in! How would vanos failure cause this? it starts sputtering at 3k and i thought vanos didnt do anything until 4.2k or so

[ascendotuum]

Look at the symptoms on this page. It operates at low rpms, and at higher rpms.

http://www.beisansystems.com/procedures/vanos_single_procedure.htm

Sent from my HTC One using Tapatalk

[franky2fingaz]

when the seals go and oil is bypassing within, you lose pressure get erratic phasing/timing, unlike Honda vtec, vanos is always phasing the cam throughout RPM

[BenM]

Is your VSS hooked up?

See here - http://www.r3vlimited.com/board/show...t=speed+sensor

[iViLe]

The rev limiter could actually be it running really rich, dodgy temp sensor and o2 sensor. with one of my bmw's I had to just leave the o2 sensor unplugged as no matter what, even with a new one, within a certain temp range it would just run so rich it would stall. I'm guessing the ecu is actually stuffed.

[RobertK]

1221 is not O2 sensor. 1221 means your ECU has tried to deviate fuel mixture rich or lean to its maximum allowed capability either due to a vacuum leak or too much fuel. I've seen a handful of bad ECUs do this as well.

If lean - check fuel pressure / check for vacuum leaks / swap MAFs.

If rich install a good rebuilt set of injectors, then check your fuel pressure for a possible bad FPR.

If neither check your CPS and vibration damper alignment. I've seen slightly misaligned dampers work fine until you hit 5-6k and cause a very similar issue but yours seems more like a fuel cut out so I'm going to guess lean mixture since a rich mixture will allow you to run it to the rev-limiter.

VSS is another possibility if your cluster is sending out a bum signal. You should be able to test that with an extra wire and a multimeter.

Vanos kicks in at lower RPM and I'm pretty positive it has nothing to do with Vanos. The ECU actually has fault codes for VANOS when it detects a mechanical jam or failed solenoid and its not 1221.

[Ryann]

Listen to Robert.

[DTFE30]

.

VSS is another possibility if your cluster is sending out a bum signal. You should be able to test that with an extra wire and a multimeter.

Bump. What should be the correct reading?