Righty ho, i have had my polo plugged in and faults cleared, but someone has mentioned the ISV (idle stabilisation valve) and changing blue temp sensor ? have taken the pipe off that goes to the ISV and apparently there should be a variation of vacuum as it should be adjusting to keep the idle, and they sometimes become gunked up, mine has very little vacuum if at all any, it now hunts at 2,000 revs and you can feel it while driving and it will sometimes slowly idle weird before flicking the battery light on or dying :D Help me please
there isn't an ISV on a G40. It's just an auxiliary air valve. It just opens up when cold and closes when as it warms up. The wiring to it is just for it's internal heater. So it wont flutter open & shut, it just gradually closes. It can cause problems if it's gunked up and stuck open or shut. Removing it and soaking it in petrol for a while will normally help.
You should leave the pipes connected, if you've disconnected one you've introduced a vacuum leak so it'll not run right.