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Fri Mar 16, 2007 12:52 pm

Hi I have a friend that has a '96 jetta trek with 2.0 litre motor with manual tranny. The idle will not stay constant. It revs up and down. If you unplug the wire at the throttle it will stop but starts hard. Help. Thanks I'm more of the air cooled types. Rob

Sat Mar 17, 2007 6:05 pm

look for broken cracked vacumm lines

Sat Mar 17, 2007 6:28 pm

If it was a vacume leak wouldn't it still do the same thing if the wire is plugged in or not? As soon as the plug is un done it will idle great which makes me believe it to be in the electrical system.

Sat Mar 17, 2007 8:01 pm

disconnect both battery cables and touch them together for a minute if that doesn't work remove the throttle body and clean it thourghly

Sat Mar 17, 2007 9:40 pm

I am guessing the thing in the throttle body you unplugged was the Idle Air Control Valve. This is a computer controlled spring like device that opens up and allows a little air to pass. Essentially like a choke, it bypasses the throttle plate and allows air to flow by. If you disconnected it and the car still ran then it is most likely stuck open. Your computer is trying to compensate for it and never can get the idle mixture it desires, hence the pulsating. Try removing it and cleaning any debris, if that doesn't work then you may need to replace it.

Sun Mar 18, 2007 7:39 am

Thanks I'll tell her son to try it, Thanks