I'm fine with the principle of the ISV. I know how they work and what to do to clean and fix them, but this is all in relation to the type in my 16V Corrado. My wife's Mk3 GTi has a return to idle problem. Runs absolutely fine until you lift off to allow it to come down to idle then it will die. Paddling the throttle for a while to keep it going will allow it to pick up to idle again and it sits there rock solid. Switches and the throttle position sensor seem to give no other obvious problem. Smells as though it could involve the ISV so I wanted to start by cleaning and checking it. I just can't see where the dickens it is! The only thing I can relate to is the vertical cylindrical valve with a connector on top, fixed to the wheel arch on rubber mounts, just behind the air filter box next to the air flow meter. This has a thin rubber hose leading from the airbox and another on to the plenum chamber just behind the throttle so it seems likely. If that isn't it then where the heck is it? If that's it, it seems a tad overly small and plastic compared with others I have handled!
the thing your describing is the carbon canister i think? me and my housemate couldn't find it on his 2.0 8v mk3 cab so your not alone in wondering where it is
I should add that, assuming I have located the ISV corectly as I described, it doesn't vibrate in any obvious way either just with the ignition turned on or with the engine ticking over. If that is it it may point to the problem. Anyone tell me what voltages should be on the pins of the connector in the Mk3? Would have expected to measure a varying voltage as the meter averages out the pulse train.
Thanks RIP_Mk3. Sounds like I'm wrong and we need someone else to help us both out. Anyone point us to an under bonnet picture to locate this?
if its a later MK3 it doesnt have one! 2e code isv is between the rocker cover and inlet manifold, same places as it is on a digifant MK2.
Thanks for the reply John, its good to have that confirmed as its an AGG engine. That seems a bit puzzling to me, its surely out of character for VW in the Golfs isn't it. Wonder what possessed them to do away with it in that model. So can you tell me how does the Mk3 deal with setting its idle then? Personally I am a great lover of my old Scirocco days where idle was stabilised with an electronic box which just sat between the dizzy and coil and read the spark frequency. If it dropped below idle it fired off an earlier pulse which effectively advanced the system and picked up the pace again until it was right. It never failed me on a number of Sciroccos and early Golfs. I've even still got one knocking around somewhere.
the idle on these is delt with using a stepper motor in the throttle body, so a dirty tb can cause issues with the idle. also if you replace the tb you will have to re-match it to the car with VAG-COM. I believe sometimes you need to do this if you clean it out?
Just to round this one off. Problem solved and easily too. A thorough clean with any old cheap carb cleaner fixed it in about 5 minutes. No adjustment needed, just undo a single spring clip, give a couple of long squirts, hook back up, and a blast to clear it afterwards. Repeat the process and its done. Many thanks to RIP and Rub for their advice, it was spot on.
