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

[javalin]

>the ISV clicks with direct current from the battery but then silent when connected
yeah.  On ISV's (that I've used before) you don't apply 12v from a battery to them, else they go bang (done that).  the ISV receives pulses of 5/12v from the ECU to control how much it opens.  Its not just open/closed, but varies depending on engine load, etc

>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
Looks like yours should be a 5v feed from DogBots autodata post....

That would explain the lack of idling as the ECU cannot control the air intake.

[DanChave]

Cheers for the info guys! In the end it was pointless to get the ISV because I tried starting it again and it wouldn't fire up! Took the spark plugs out and they were black, checked for a spark and there was one  at first turn of the key and then nothing, connected a spark lead and plug straigh to the coil and still no spark! Each time, the plugs were grounded on one of the cam cover nuts.

So no, its not fixed

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!

Yeah, I adjusted the throttle cable to bypass the ISV so I could perform some checks to see if any differences occured ie, depressing the idle switch, pulling out the ISV, disconnecting the ISV to Air Box breather etc. from what I can tell, the micro switch works and the wiring to it is good/repaired, removing the airbox breather made no difference (meaning the ISV is in the closed position?) But pulling it out made the sudden rust of air stall the engine (confirms ISV closed?)

[DanChave]

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

The plug is getting power and I have checked fuse 15, which is fine! Unfortunately, my oldskool multimeter just tells me if there is power or not lol! I will go out today and see if I can get hold of a more modern one.

I am downloading AutoData at the moment but it is taking a lifetime, could you dig out the values for the other plugs as well for me please?

[DanChave]

>the ISV clicks with direct current from the battery but then silent when connected
yeah.  On ISV's (that I've used before) you don't apply 12v from a battery to them, else they go bang (done that).  the ISV receives pulses of 5/12v from the ECU to control how much it opens.  Its not just open/closed, but varies depending on engine load, etc

>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
Looks like yours should be a 5v feed from DogBots autodata post....

That would explain the lack of idling as the ECU cannot control the air intake.

I just put the ISV to the 12v to see if the valve was stuck. we did this initially while the engine was stripped down, maybe this blew the ISV in the first place, hence why it wont idle now? School boy error on my part I guess

I will get hold of a better multimeter today and check the actual values that the different plugs give out.

[javalin]

easily done.   

worth checking the cam/crank sensor is attached and working else no sparks will be triggered.

[DanChave]

Cool, I'll check that as well. Although, it should be fine as I replaced the crank sensor with a new genuine part when I built the engine back up!

[DanChave]

So, I checked all the Volts at each plug and I got the following

ISV                        - 0v/0v
Throttle Microswitch - 10v
TPS                        - 3.5v/0v
Crank Sensor           - 10v/10v
Knock Sensor           - 0v/0v
Anti Knock Sensor     - 10v/10v
Coolant Temp Sensor - 3v
Coil Pack                  - 12v/0v
Hall Sender              - 10v/10v

In regards to the ISV reading, I then replaced fuse 15 (the fuse in there was still intact though) to no avail. Next step I guess is to check the wires from the ISV plug back to the multi plug and check the corresponding pins there as well.........

If anyone could did out what the correct readings are, for the other plugs, that would be great. I'm still waiting for AutoData to finish downloading

[spikenipple]

Whoever mentioned fuse 15, I f*cking love you   
Just sorted this idling problem thanks to you, it's been the bane of my life!

[DanChave]

Whoever mentioned fuse 15, I f*cking love you   
Just sorted this idling problem thanks to you, it's been the bane of my life!

I wish it was as simple as that for me Glad this thread has helped someone else at least though!

[Leon27]

Autodata says to test the ISV unplug it and test it directly at the ISV - You should get 3.5 - 6 Ohms

For your reference:

Crank sensor supply voltage - Pins 1 & 3 - 9v
Cam (Distributor) supply voltage - Pins 1 & 3 - 10v
Throttle position sensor -  Pins 1 & 3 - 5v
Coil - Pins 1 & 3 - 11v min

Coolant temp testing gave a table of resistances not voltages.