90 tsi drives fine, then lights dim, sputter, won't boost

[Well Traveled]

Ok, my 90 tsi is acting up. A week ago, while driving, it starts sputtering and the lights start getting dim. I also noticed if I tried to boost, it would miss and buck. I got it home and it died in my driveway. I couldn't get it to start. It clicked, so I replaced the battery. That fixed the problem for a week. Tonight, it did the same thing, but didn't die, just idled really rough. It won't boost and the lights are really dim. Any idea what is going on here?? Alternator?? ECU?? It confused me that it worked for a week after replacing the battery. Any help is appreciated.

 

[IHeartTurbo]

Chances are it's the alternator or the wire's between it and the battery. Or your missing a belt.

 

[dalepmay]

It's the alternator most likely. The reason it worked for a week after you replaced the battery is because for that week, the new battery was the only thing keeping it running.

Here is a little tip for anyone who doesn't know: To check your alternator, start your engine, and with the engine running, disconnect the negative wire on your battery. If the enging keeps running without any difference, the alternator is fine. If the engine dies when you disconnect the wire, the alternator is bad. Tachnically, you should be able to have the engine running, all lights, radio, heating, etc on and the battery should be able to be disconnected and the alternator should keep everything running. If not, you need a stronger alternator.

 

[Well Traveled]

Alternator fixed the problem. Thanks guys