Alright so I have a 1997 jetta glx vr6 and after a winter of being under a cover I decided it was time to get it back on the road. The battery was dead after 6 months of sitting so I gave it to my mechanic to charge it up for me. I took a battery out of a pickup I have and have been using this battery. Until now (about 4 hours after I put the battery in) it worked fine. My car just wont start. So I jumped it, and it started, but the only way it would stay running is if I keep on the gas. Does anyone know whats up with it?

C'mon someone has to have an idea??

Starting in '96 the VR6 engines used an electronic throtle valve rather than a cable to the gas pedal. When the battery is disconnected the ECM will lose the basic settings for how to control the throttle, most of the time it won't even be able to start. I cannot explain why it ran for four hours or why it would start when jump starting. But it does explain why it will not idle. To properly reset the ECM requires a VW scan tool or simulator like the VAG-COM, check out this thread on the subject.

http://www.asashop.org/autoinc/oct2003/techtips.cfm

thanks for the info