16v idling problem...

[spikenipple]

Hi all,
I've recently picked up another valver and am having a bit of trouble with the idling.
The only way I can get it to idle is to pull the ISV out and leave a little gap between the bung and the inlet manifold, otherwise it will cut out every time.
I have tried 3 different (known to be working) ISVs in the car and it's exactly the same so i know it's not the ISV that is directly responsible.
I've thoroughly cleaned all of the breather pipes, checked the idle bypass holes in the throttle body for blockages, changed the throttle position sensor to a known working unit, all with the same result. I have also tried with/without the throttle stop sensor (engaged when throttle is at 0%), air inlet temp sensor, various air pipes on/off to no avail.

Can anyone suggest what to try next?  

[Ess_Three]

Have you checked the wiring behind the head, over the exhaust heatshild, that goes to the throttle pot?
It could be that, or the wiring for the idle switch?
Sounds like it's maybe the idle switch circuit...possibly the switch not making, or the wiring open circuit and it's not asking the ECU for the idle map?

[spikenipple]

Good idea, thanks bud, i'll get the multimeter out and give it a go when i get a minute spare. Fortunately my daily is another valver so i can check the two against each other 

[spikenipple]

Ok seems like there's no voltage to the ISV when idling. Checked fine for continuity between ISV plug and large circular loom plug in the engine bay, looks like i'm gonna have to dust off the old Haynes manual and work my way back to the ECU....what a ball ache!

[Ess_Three]

Did you check the idle switch & wiring?

Are you sure the ISV is being called for by the ECU?

[spikenipple]

I've just been out again and checked the idle switch on both cars, both are getting 11.50 volts to the idle switch (ignition on, engine off).
I'm getting no resistance or continuity on either idle switch in both open and closed positions.

I checked the resistances/voltages across the 3 pins on the wiring for both car's throttle position sensors with the ignition on and engine off, they are as follows:

My daily valver
Pin 1-2 0V 0.0 ohms
Pin 1-3 5V 5.82k ohms
Pin 2-3 5V 6.84k ohms

The troubled valver
Pin 1-2 19.3mV 0 ohms
Pin 1-3 5V 5.82k ohms
Pin 2-3 4.8V 5.92k ohms

I don't know what the differences mean between the two but it could be something?

I've ordered a VAGCOM which will hopefully turn up within the next few days and reveal an issue, but otherwise I'm pretty stumped 

[KUR2Y]

I had this recently and found an open circuit between the ISV and the ECU. White wire to pin 21, I think.

[spikenipple]

Hopefully the sun will still be out tomorrow, I'll give it a bash in the afternoon thanks

[spikenipple]

Ok a little update;
I've found that a 3-wire cable running through the engine bay is completely shagged, and I think this is the problem.
The other problem is, I don't know what's plugged in at the other end.

The top end of it is the bottom plug on the 3 vertically stacked plugs, in front of the large circular engine bay loom. The wire runs down and to the left, then comes back up and connects to something behind the oil filter. I can feel that it's connected into some sort of sensor, but I don't know what it is, and it seems to be hard-wired so I can't just pull it out and replace the wires!

Does anyone know which component this cable serves, and how hard it is to change?

[Screech16v]

Sounds like your crank position sensor,normally have to support the engine and remove the mount unless you got a hand like jeremy beadle