funny idle problem

[benji mk2]

Have had a little search but cant find anything relative to the problems i'm having.

 Car is an 8v PB gti with a 2.0 bottom end, fast road cam, induction kit and 4 branch. It has recently started reving up of its own accord. Its only slight but a bit annoying, when pulling up at junctions the revs drop to normal idle then slowly increase to 1500 rpm, it then drops to idle and go's up once again. It always seems to do this twice. I'm gonna try and do rubjonnys pb tuning guide when i get chance, just wondering if anyones got any ideas???

[Blazing Storm]

I have been getting the same problem, as of late, except mine doesn't have a 2.0l bottom end. Will be interesting to read people's suggestions.

[Leon R]

A few parts can cause this, on my valver this happened due to air leaks which i sorted, then it happened again! The cause was the Idle Valve, it was quite dirty with oil and probably restricted the air to idle the car.

Get a tin of brake cleaner/carb cleaner, remove the idle valve completely off and spray the solution into the exposed holes of the Idle Valve. If the solution drips out black then you know its dirty so keep spraying it until its clear.

Before you refit it to the car, make sure the brake cleaner is pretty much evaporated out.

[benji mk2]

cheers for the info Leon R, have tried what you recommended with no joy. Can the isv be removed and cleaned?

[smithysmoo]

Mine does the same gonna get the ISV off to clean as soon as I get chance.

[vin1.8t]

i had the problem with my 8v i took it in the garage and got it sorted
i was told it was a wire that went to the manifold?
but it dont do it now

[tenebrae]

Same problem, cleaning the idle valve had no effect, so hunted down a spare on ebay and bobs yer granny, sorted.
Made a habit now of grabbing these valves when i happen to stumble across a mk2 in a scrappy, like yesterday as I hunted out some clocks, sadly some get had got them first....the rat fart...still, small enough to stuff in a pocket and claim as a freebie..! nice..
Teach em for letting someone get there first...bloomin clocks, replaced the cable, great! two days later the speedo fecks up...karma I guess..

Rick