This is what happened. I installed an amp for a sub woofer in my friends car and it sounded great and all. Started fine the next morning and he went to work. he called me later on and said his car wont start. i figured something slipped off and they're may have been a battery drain, but i didnt tell him that. i told him to take out the inline fuse that i installed for the power for the sub to try to get rid of the battery drain. he tried to get a jump on his car come to realize that the battery wasnt dead it was just a loose battery terminal. he didnt figure that out until after he tried to jump it. i dont know for sure if this would mess anything up but i suppose that the extra voltage in the power system fried something. now the car starts fine but but the check engine light is on and when you try to accerate past 20MPH or about 2.5-3K RPMS it dies and revs down until the speed comes down. i am not familiar with volkswagons at all so i do not know what to check. but its a 1999 Jetta 2.0L GL. any help would be greatly appreciated. thank you.

--Zach

You need to get the codes read.

Sure sounds like you fried the ECM. These VW's suck so bad. Don't even get me started on mine. In short, it started acting up the next I brought it home brand new. Dealers giving me the run around and all. It sucked!

Now You know what's f--k'n weird? The next day the car ran perfect. We didn't do anything besides leave it in the garage overnight.... and now it's running fine. The control modual must've reset itself, or something...

Sounds like what happens when a coil is bad. My 00 jetta vr6 does that when the coil is bad and it gets wet. Take it to autozone or pepboys or similar and have the codes read. VW's Rock, they just have a bit of personality that takes some getting used to.