ISV causing misfire...?!?

[sKrEwBaLL]

Yes, the rev counter was jerking about all over the place and the car was undriveable

[Gambit]

this is exactly the same as what happened to mine, farted banged misfired big puffs of smoke out the back, rev counter bouncing all over the place

replaced dizzy, hasn't done it since, also check all electrical connections for damp, green mould etc

with the ISV disconnected i just idle of the idle screw which is perfectly fine

ISV only compensates the idle when under load from the likes of rear window lights and fan all being on

[Blue MK2]

Mine was bouncing all over the place. Got my coil changed and it went away

[sKrEwBaLL]

I think I'll get my idle sorted using the screw and just leave the ISV disconnected.  Its more hassle than its worth I reckon  

[golfvr6]

If you are running the car with the idle valve disconnected then you probably have an air leak somewhere.

[sKrEwBaLL]

I think you may be right, but I'm not sure where the leak is

[richandhazel]

If the rev counter is going all over the place that would tend to indicate an ignition problem. Could be that disconnecting the ISV is disguising the real problem.

[richandhazel]

Don't get me wrong as it could still be a vaccuum leak but I think I would try what Gambit has suggested and check the ignition side of things first.

[golfvr6]

Yep i'd go along with that, the hall sender seems to be always worth a look.

[?lauf's Chariot]

It shouldn't hurt leaving the ISV disconnected, assuming the engine's idling ok. the ISV only saves the car from stalling, if the engine hunts, you'll hear it clicking. If it wasn't clicking before, then it probably isn't doing much, mine works fine without. With vacuum leaks though, you really have to check nearly all the hoses except cooling ones. Takes a long time, and is a real pain in the arse, try the simple things first!