ISV ? Air leak ? Power surges ?

[workhorse '90 8v]

I've got a bit of dodgy running witha '91 8v.  Idle can rise and fall, and sit too high sometimes.
Also when driving, there are small surges of power pulling the car forward.

I figured this could all be down to a vacume air leak somewhere?

The timing has been done, so it's not that.

Now then, while a dirty ISV will affect the idle, can it also have a affect whilst driving along at say 2500rpm??  (surges in power - from extra air??)

I'm gonna clean the ISV and air flow meter with carb cleaner sometime.  And maybe have a search for any kind of leak in the vacume hoses..

Anyone got any ideas....?      thanx J.

[Mr Blue]

do you mean its 'pinking'? i have this when slowing down to about 50-60mph and its scarey sh!t

i would say its an air leak but i dont think its to do with the ISV

[workhorse '90 8v]

isn't 'pinking' a slight, er,  pinking noise coming from the engine ??

this power surge is only small, almost like the choke is kicking in  ()

[Mr Blue]

pinking as a judder fromt he engine.

[workhorse '90 8v]

not a judder.  just a pull from the engine as if the accelerator has been pushed a bit..

i'm guessing an air leak.. i'll have a search about............