I have just had a very similar sympton with my own car.
It turned out to be a missing plug on the left hand side of the inlet manifold (as viewed from the front of the car).
There is a small tube which leads to the fuel injector rail and right next to it there is a spigot of about 10mm diameter.
Somehow I had managed to lose the plug when I was changing the cylinder head.
I managed to get a suitable replacement from work and fitted it, after that all was well.
Hope this helps,
I appreciate your reply.POssibly the idle control vale or coolant temp sensor - does it get better once the engine is warm?
Coolant temp sensor i think is on the right hand side of the engine (looking from the front of the car) If its anything like the 16v version of this engine then the icv is separate to the throttle body.I appreciate your reply.
No it doesn't get better. I've changed the whole throttle unit for another one and didn't make any difference so I think the icv is ruled out. Where's the temp sensor and how do you test it? Just pull the wire off?
Somebody suggested that it could be the ECU.
Does that sound feasible?
It turned out to be the one on the right and I got one from the scrap yard for a pound.