Is my ISV faulty? (I have searched the forum)

[Maltloaf]

Before anyone says anything I have changed the blue temp sensor (gen VW) and searched many forums including this one.

I had a problem with my PB digifant which seems to point to the ISV, the revs started to hunt between 1000-3000 then sat at 3000 on idle. Now it does not drop below 3000 at all warm or cold starting.

The throttle switches have continuity, the ISV clicks and also has continity and has also been cleaned and I could not find any vacuum leaks. But what I did find that if I took the pipe that goes from the inlet manifold to the ISV off and pluged both ends then the idle almost returned to normal once the engine was a little warmer anyway.

Would this suggest that the ISV is faulty or that the ISV is getting an incorrect signal from the ECU?

Please help, I have only just rebuilt the engine and now this is playing up.

[Diamond Hell]

If you're about this weekend I have a couple of known-good ISVs you can try.  I'm in Filton.  PM me to organise, if you want.

[Organisys]

Have you checked the actual wiring to the closed throttle switch on the underside of the throttle body?

otherwise Sounds like the ISV (does it buzz ?)

If neither of these, could maybe be a fried ECU although I think this is uncommon.

[Maltloaf]

The supply to the switches it about 4.98volt just under the 5v and I gave it a good wiggle to see if there is a broken connection but it seemed to be ok.

The ISV used to buzz a little bit but it only seems to click now when the ignition comes on, I tried another ECU and that seemed ok.

I think I will go for the faulty ISV and try to get hold of another one.

Thanks

[shikta000]

my moneys on your isv....this happened to me recently..i also checked the throttle valves for continuity..same result as you....after checking all the usual suspects i came back to the conclusion that if your isv dose not 'buzz' or vibrate when ignition is turned to the 1st position..its gone to isv heaven..i keep a spare now..saves all those checks.

[Maltloaf]

I am starting to think I should have a second car in bits in the back of the garage for testing!

[dabill]

might be a plan... in all seriousness!

[Maltloaf]

Just incase anyone is interested or has the same problem as me. Replacing the ISV fixed the problem and after a quick tune up at TSR it running better than ever.

Thanks for the help guys.