MK3 Golf GTI 16V Stalling below 1200rmp.......

[DanChave]

Cheers bud, I give him a shout

[Leon27]

Run the engine, open the throttle by hand enough to touch the idle switch and the engine running will noticeably change.
Release the throttle and make sure that the mechanism goes back and then touches the switch you were pressing.

If it doesn't touch the switch then the switch needs to be aligned again
If the engine running does not change then this may indicate a idle switch/wiring/ISV issue

With VCDS also check the coolant temp status just to make sure everything matches up. How did you cure the hesitation and cutting out problem before the rebuild?

[Dogbot]

Just to add, I discovered recently when putting my abf into the mk2, that just because the ISV buzzes doesn't mean its working! I had to try 4 (from breakers) before one worked, all the time I was sure it wasnt the ISV an searched for something worse but my friend who is a specialist with vag cars was adamant it was ISV.... Yet I was lost how I could have 4 buzzing ISV and only one of them allow the car to idle! 

[DanChave]

Run the engine, open the throttle by hand enough to touch the idle switch and the engine running will noticeably change.
Release the throttle and make sure that the mechanism goes back and then touches the switch you were pressing.

If it doesn't touch the switch then the switch needs to be aligned again
If the engine running does not change then this may indicate a idle switch/wiring/ISV issue

With VCDS also check the coolant temp status just to make sure everything matches up. How did you cure the hesitation and cutting out problem before the rebuild?

Thanks for the advise, I'll open the throttle by hand, enough to depress the microswitch with my other hand and see if there is a change! I only have VCDS Lite, so I don't think I can check the coolant temp etc, but I'll look into it as well. The hesitation was caused by worn vac lines and a damp ecu from all the years of wet leaves under the scuttle panel, the cutting out when warm was a suspected ISV problem before hand, but when. I checked it and it buzzed and clicked in and out I presumed it was working and it was more likely to be a wiring problem. After checking the wiring and soldering up a fracture, then checking there was power at all the plugs with a multimeter, I think I have ruled that out now so back to ISV or idle microswitch.......... Hopefully today I can borrow a mate's ISV from his corrado G60 (he has a spare as well) and we'll see what happens lol!

[DanChave]

Just to add, I discovered recently when putting my abf into the mk2, that just because the ISV buzzes doesn't mean its working! I had to try 4 (from breakers) before one worked, all the time I was sure it wasnt the ISV an searched for something worse but my friend who is a specialist with vag cars was adamant it was ISV.... Yet I was lost how I could have 4 buzzing ISV and only one of them allow the car to idle!

I know, its bizarre right! All I can think is I know there is a few different part codes for the ISV's used on different models and maybe they allow different tolerances of air through? Either that or even when you can here the needle clicking in and out, its not opening/closing to its full potential? Bloody things.

[Dogbot]

I know, its bizarre right! All I can think is I know there is a few different part codes for the ISV's used on different models and maybe they allow different tolerances of air through? Either that or even when you can here the needle clicking in and out, its not opening/closing to its full potential? Bloody things.

Damn right it's bizarre!  I only used mk3 items to rule out any differences between the mk2 and 3 although physically they look the same, but like you say I'm not sure of the opening tolerances, however I did notice all of the ISV I have each have different buzzing sounds!! Some loud some quiet and the one that's working I have to put a stethoscope to hear it buzz!! I'm still not convinced they are all buggerd because we tried some on another abf an 2 of them worked, however the one on my mk2 abf didn't work on my mates abf in a mk3, the car is acedimic, the dam things should all work the same as they are mk3 an the part numbers are the same!! Far too hit and miss could be the age of them tho! The 4 I have we're all checked working on my engine before removal from mk3, left in the tool box for a few months an now it's the ISV lottery!! Poxy  things!! Lol

[DanChave]

Feel free to send me one

[DanChave]

I managed to get the car to idle today by adjusting the throttle cable at it's tightest setting so the micro switch wasn't depressed. This allowed me to test a few things, I was able to depress the micro switch whilst the engine was running to see if there was a change, which there was! So, idle switch and wiring are ok I also disconnected the ISV breather,  with no effect, meaning the ISV was stuck closed? I then connected the ISV straight to the battery, I could hear it click but made no effect to the running of the engine. then I pulled to ISV out of the inlet and the engine stalled, I am 99.9% sure it's the ISV, I bought one from Ebay and I'm picking up one from Plymouth later today. Hopefully It'll work, I can't wait to have it drivable so I can get it up to Volkscraft in Exeter and get the timing light on it and check it all over

[Leon27]

Did the new one make a difference? Hope it is working!

Just to confirm does the throttle mechanism on idle touch the idle switch? If it does, that's how it should be. From what I read, you adjusted it so the throttle was open? This bypasses the need for the ISV as the engine is getting it's air supply from the open throttle, when the throttle is closed only then should the ISV kicks in.
By removing the ISV you created a big air leak, enough to stall the engine I'd assume as the fuelling wouldn't cope.

If the throttle set-up is ok, switch and wiring are proven to be ok and you are still having problems I'd check the voltage supply to the ISV if you haven't already. You are giving it 12v from the battery but maybe the ECU isn't?

Hope it's all working anyhow!

[Dogbot]

Auto data says there should be 5v at the ISV plug when the ignition is on, I would check this, if there's nothing at the plug fuse 15 is at fault