Help Car Wont Idle. 1996 Mk3 GTI 16V

[Andys Work In Progress]

Urgent help required.
My MK3 won't idle unless i remove the pipe from emission controls to throttle body. Any ideas were to start would be great.
Thanks in advance.
Andy

[itavaltalainen]

ISV operational?

[Andys Work In Progress]

Sound like its working and when you remove pipe from throttle body and restrict hole (but not fully) you can get a stable idle of about 900 to 1k rpm. The car has been apart for the best part of two years now on way back together and this issue is stopping everything as want engine running before progressing any further. Help.

[LR5V]

If you block the pipe fully does the engine die?
If it tries to keep running you need to check for air leaks, I had an idle problem with my vaver, took me a couple of months to work out what was going on...

It was self inflicted, I had stripped the threads by over tightening the bolts holding the upper inlet manifold to the lower -easy done as they are a very low torque. this allowed un-metered air into the engine, it was ok cold but hot it would idle at about 1500 and sometimes the revs were pulsing up and down from 1500 up to 2000 -looked like a total nut during rush hour queue's. Swapped to an undamaged lower manifold and all was good again.

The vacuum pipes like to turn to powder and cold be your problem, replace them with silicone -especially the one going to the engine ECU in the scuttle.
Try cleaning the ISV with crab cleaner.
Check the wiring loom going to the TPS above the exhaust manifold, insulation gets crispy and the wires end up bare & short out on each other.

[Andys Work In Progress]

Car cuts out completely when you fully block pipe. Tried wiring and yes it was All clusty so repaired wiring but still no difference so cleaned isv (load of gunk came out) but still no difference. Doesn't seem to have a vacuum pipe to ecu. Any idea if it should have one and if so where it fits?

[Simeon]

On a 1996 ABF the ECU vac pipe should be attached to a nipple (oooerr) on the back left hand side of the inlet manifold.

[Andys Work In Progress]

I can find vacumm nipple on inlet manifold but not on ECU is it a case of cant see the wood for the trees or am i just no looking in correct area. Has anybody got a picture of said pipe going into ECU so i could use as a guide.
thanks everybody so far for advice. Finger crossed i get this sorted soon wanting to get the car to VW festival this year. Andy

[Simeon]

The vac nipple on the ecu is literally next to the mulitplug from the loom. If you loosen the mountings of the ecu and look you can't miss it

[Andys Work In Progress]

Found it, reconnected it and!!!! still no difference. Argh this is begining to test my resolve. Think i need nice person with vagcom to rescue me. thanks again for all your advice.

[Simeon]

That's a shame it didn't sort it. Have you replaced all the VAC hoses? Might be worth doing in case one is split somewhere.

Have you checked the static timing? I know its highly unlikely, but it would only take 5 mins to check, and I once had an idle problem on an abf which was finally found to have been caused by the crank pully moving on the crank nose.