E30 Zone

Hi Guys,
I've a 1988 320i cabby that runs perfectly until it reaches about 5000rpm in any gear - when it feels like it hits the rev limiter and won't rev any higher - just when things are getting interesting.
The problem is independent of throttle position or engine load. Don't think it's fuel supply.
I've tried a different ECU (from same model) - no difference.
When I first pulled off distributor cap and rotor, cleaned & re-assembled, it revved up to 5500 a few times before settling back to where it was before. Strange...
After that I replaced dizzy rotor, ignition leads, dizzy cap; checked and cleaned all connectors. Still no joy.
Plugs look OK.

Could it be Crank Position Sensor? I've pulled it off & given it a clean but not replaced it yet.
Feels like an ignition issue more than worn camshaft or something (engine feels strong & only done 110,000)

Anyone solved/had this problem?
Ideas gratefully received. Thanks

I had a 1984 B-reg L-Jet 320i, which ran fine until I took it Halfords for a new cambelt and it did the same thing afterwards; I reckon they fitted the belt one tooth out.

Hmm...interesting. Mine just had new cam belt fitted too - not Halfrauds though - someone I trust, so should be OK. Wouldn't it run pretty badly through the rev range if cam timing was out?

Mine ran fine, until you got to about 5,000rpm ish, when it just wouldn't go any higher.

Did you get it fixed?

No, in the end I just put up with it for a few months then sold it.