4500rpm false rev limiter.

[Qirex]

Posting here as the tech forum is very quiet...

 

I have a uk '03, 115k, generally in good mechanical shape. I changed the clutch last weekend  at a friends place and due to rot on the exhaust I fitted a Scorpion Y pipe and some generic sports cats while doing so.

 

Test driving afterwards I was slowly adding load and came to a point where I was stretching it out. In third and fourth at 4500 rpm at high throttle angles I hit a rev limiter. A harsh sudden and complete power cut, not the slurring power reduction of an ASC event.

 

It was concerning as it put huge driveline shunt into a brand new clutch. However it seems to be ok...

 

I came back, shut down, restarted revved in neutral and it span to beyond 4500 happily. So, I drove home later and the problem had gone. I'm yet to see it happening again, but I commute in other cars or on foot, I'm hoping to test today.

 

So far I've checked the intake and exhaust for leaks and nothing found. No stored DTCs in the ecu either. I'm thinking of taking it in to see if there's any stored abs system faults, but might be a few days before I can.

 

My suspicion is an electrical fault, anything on the air management side capable of causing a hard stop on the rpm at 4500 would manifest in other ways too, and currently it starts and idles fine.

 

I found some old posts mentioning vaguely similar situations, but no solid conclusions.

 

Has anyone seen this before?  Or any thoughts on what might be happening?

[Qirex]

Just a quick update, it's not yet done it again. Which is simultaneously excellent and terrifying. Should it ever return, I'll bump with the solution...

[Jetpilot]

If there is no engine management light and subsequent code to read, most of us would be taking a punt as to what it is, however, after installing a new clutch i had problems with a crank shaft position sensor that worked fine with the old clutch but not with the new, that would be my first port of call being you swapped the clutch, but i cannot 100% say thats the problem.

[Qirex]

Ok, so it's at it again. Similar symptoms, 4500-5000rpm rev limiting. Less abrupt feeling than the first time. Either my familiarity with the event, or in the dry there's less wheel slip occurring as the torque spikes.

 

Investigation is ongoing, but a clean and check of the crank sensor seems to have had no effect. Next step is to refit the oem cats and continue with tidying it up. Might consider a crank sensor change, but until the issue is chronic, it'd be impossible to tell if it fixed it.

 

I'll update with any new info when I have it.