try a compression test, maybe a sligthly blow head gasket. cheers

Hi, thanks, 1 and 2 aren't firing at idle, the dizzy is locked and has no vacuum advance,

Thanks for the quick reply.
Simeon.

Pull the leads at idle one at a time and see if all 4 are sparking (most likely are) so it could be a fuel air issue?!

Possibly a vacuum leak so at high inlet vac. situations it sucks too much air to burn (ie when the throttle is shut)? Just a thought.

I have a worked a12, at low revs it runs on 2 cylinders, but when i increase the revs it suddenly jumps into life and runs on all 4.

I have just fitted new leads, new dizzy cap and a new rotor, and the spark plugs seem good

I have checked tdc against the dizzy, and the firing order is 1-3-4-2 (right?)

still don't understand what it is.

Please help.

Thanks,
Simeon.