Engine problem developing any ideas?

[jondee86]

phill 92 Wrote:About 2 days ago I pulled up at some traffic lights and for some reason, I
have no idea why, I slowly built up the revs whilst I was waiting (I was
waiting a while and was very bored). Anyway I was building the revs to
like 4k really slowly (like just resting my foot on the pedal) and the
second time I done it I got to 2.5k and then suddenly the revs dropped of
really quickly and before the needle could reach 1k it shot back up to
where it was before. I was like oo what was that so tried it again and the
revs built up as normal so tried again and it done it again. by this point
the light was green and I drove off.

This one definitely sounds like fuel cut. The throttle was so close to being
closed, that the ECU thought it was closed. High manifold vacuum, closed
throttle and revs above the threshold = fuel cut.

The other stumble will be something else.

Cheers... jondee86