AKCJ

The cutoff at a certain rpm makes it sound like a barn door slide issue. I would pull the cover off at the afm and check it out. If that's it you can fix it. I once had a bad electrical connection at the afm plug that was causing a stutter so check that out too.

Another idea would be to check the clearance at the speed & ref sensors. Or what if one of those sensors is weak? I would not think that's the problem but I would at least check it out.

How about a weak connection in the DME (solder joint).

Just throwing ideas out.

User 52121

Could it be something like a bad CV joint skipping/slipping while under load? Are there splines back there that could be worn out?

LP944

I have not checked any of those and will check them as soon as I can. Before the harness replacement I had starting problems but the stuttering and hesitations came about afterwards.

Mello

On my 951 I had two problems that were both solved by putting in new Speed/Reference sensors.
1. Randomly would not start at times from anywhere between 5 minutes to an hour. (no tach bounce when cranking)
2. When pushing hard on the highway, power would cut out momentarily around 5K rpms.
No other symptoms.

LP944

Sounds very alike to mine, accept I havnt dared redline it to find out if its momentary, which i dont think it is. I found out today that it lowers with every RPM, 3rd-5700 4th 5500-5400, 5th 5400-5000
Is it a quick and east fix? Did you have hesitation in mid RPM range in low gears?

Mello

I didn't have any other symptoms. Reaching the sensors on my 951 was easy enough with a u-joint on a looong extension. I just took out the sensors, not the bracket for them. Don't touch or accidentally loosen the bracket for the sensors or else you have to re-set the depth of the sensors. I just popped out the old sensors, and popped in the new ones without needing to adjust anything.
Actually, one of the two sensors I believe is the culprit, but they're identical so I just replaced both.

LP944

So when there was no power there was no sound?
Thanks for the info

Mello

This was 7 years ago... but from what I remember there was no sound. The power just cut out for a second and would come back after I let off of the gas.

LP944

No mine doesnt do that, it like hits a wall in the power band and stays there till redline

Mello

I don't understand how it could hit like a wall but keep climbing to redline. Anyway, the problems are very similar. Worth a shot to try to try new sensors. Can always return them.

peanut

I don't believe your sensors are faulty. If they were you're car wouldn't run at all. The ECU needs to receive a 200rpm signal from your crank sensor before it will earth your ignition system and earth your DME relay supplying the fuel pump and fuel injector supply.

if you are going to do this I would strongly advise you to cover all the openings in the clutch bellhousing with gaffa tape first. There are plenty of members that have dropped nuts, sockets and spanners into their bellhousing .!

If the sensors are oxidised and stuck in the housing you are going to end up in a right fix because its such a pita to get at the b$%&* things

I would do the sensor test outlined on Clarkes first and establish beyond a doubt that your sensors are no good first. All they are is a simple magnet ! not much can go wrong with a magnet to be honest

931guru

If you're having a misfire at 5500 rpm, it is quite likely that you have a broken valve spring. Unfortunately, you have to remove the camshaft housing to find it. Just push down on each valve and the one that moves with only thumb pressure is the culprit.

If you use either the compressed air or the rope in the cylinder method, you can replace the spring without removing the head.

LP944

Thanks for the info. ITs not too hard to remove the housing is it?

peanut

do a compression test first ! it may not be conclusive but should indicate a leaky valve if a spring had bust. I'm not convinced myself. I think you would get some symptoms long before the engine reached the red line

LP944

Could it be the ignition module?