I have had bad idle for a long time, especially when the engine is hot.
It might be the icv, my mechanic have tested the output from the ecu, a Haltech platinum sport 1000, and have found a constant voltage.
Is the phase 1,5 icv voltage or pulse regualted?

 

Anyone?
How can I test it for function and exclude ECU-fault?

 

have you had it apart and checked the seal/gasket?

http://forums.nasioc.com/forums/showthread.php?t=781242

 

Thanks for the link.
But I have the phase 1,5 (MY97-98/v3-4) iacv which is different.
So, maybe I'll try to take it apart, but the instuctions in the thread won't help me much.

 

Hi Adam, My car has recently developed a very lumpy idle and partial throttle lumpiness that I put down to an intermittant misfire - now I'm not sure if I am barking up the wrong tree?? It started as an occasional miss but then got worse after a run and heat built up. It doesn't happen every time so that makes it hard to find!!

Anyway, I have the same ICV as you and I cleaned mine by undoing the four bolts and lowering it away from the manifold, this was to avoid undoing the water pipes that feed it. There is a horizontal plastic tube with a slot in it. mine rotated easily but I cleaned it with brake cleaner and a cotton bud - made no difference. I have checked whether it makes any difference by unplugging the electrical loom on top, the idle then rose to about 1500 and when plugged back in the revs dropped, therefore it works but I cant be sure it works exactly as it should. There is obviously some feed from the ECU when the A/C is used but as my problem is not always there I cannot replicate anything to make it start or stop!!

Don't know if any of that helps but I share your pain!! And at about £270 for a new one its not a cse of buying one to try either