Car revs die when trying to start it??

[Jakarmy]

 
Just started to do this within the last few days. Turn the ignition key, car starts, but immediately the revs drop to nothing and the engine dies. It might start on the next turn of the key, or this could go on for another few times before she eventually starts. Car is running great, no misfires etc.
Any ideas would be welcome before i start spending loads of money on things i dont need.

Thanks in advance

[oggy]

check crank sensor (hall sensor) on distributor rotor shaft  -  see mk3 johnny post

[Len]

Also worth a look are the vent pipes around the manifold and up to the ECU.

[boneybradley]

Or ecu temp sensor?? cost about £10 and take 2 minutes to fit