Runs for 30 minutes....

[Morat]

This is getting strange.

The Symptoms.

Car runs fine from cold. Idles at about 900rpm pretty stable too. Performance is good, with a good pickup from low revs. Revs cleanly round to the redline without any hesistation.

Then, as long as you rag the car it seems fine but if you run at a steady speed at part throttle things start to go pear-shaped. You can be doing a steady 50 in 5th and the car will miss. It starts as a slight hesitation and then proper misfiring. Idle goes to pot at about this time too, rises to 1200 then if you sit there with feet off it will surge up to 2k and back all by itself. If you dare touch the accelerator at this point it will cut out and will be a total bastard to start again (you have to leave it for a minute and crank it for about 30s and hit full throttle as soon as one cylinder fires).

If you keep going the car gradually overfuels more and more, cylinders drop out until you're down to 3 and then its all over until either you rag the car to the redline and back a few times or you let it cool down.

What I've tried so far.
Checked Hoses - replaced the big intake boot
Replaced Blue temp sender
Replaced ECU.

It doesn't seem to have made a lot of difference, although the new ECU is better than the 320i one which was better than the original...

It still isn't happy tho. Any thoughts?

[Chris-W]

I'd look at the distributor cap & rotor, then the AFM.

[Martinaston]

Then the wire to the crank position sensor,clean the ICV then check the HT leads.