My engine warning light is on, tried re setting ecu and it still came bk on, have noticed now that if you rev the engine as the revs drop the engine nearly cuts out and the picks itself back up again

anyone got any idea what this could be

i have a x reg, 2.0 esp focus

cheers

 

Quickest way is to code read it.
Most likely a sensor gone duff.
tabetha

 

Sounds like ISCV a quick removal and cleaning could fix it.

Is it missfiring at all when revved? coil-packs are very common.