Random car stalling

[91dsmtalon]

I recently bought a 91 Eagle Talon Tsi AWD, it sat infront of my house for about a month before it became my daily driver. During that time I would drive it just to make sure it all worked right (once a week). I was finding the battery could not a hold a charge, and I would frequently have to recharge the battery. When the time came for me to start driving it every day it started out fine. Than all of the sudden the car wouldn't start after driving over to a buddys house. So we jumped it and it started fine, I was able to make it a few miles before the car stalled and died in the middle of traffic, I had just enough time to make it a gas station stall. After letting the car sit for about 20 minutes and getting another jump I was able to make it home (another 2-4 miles). Thinking that the battery could have something wrong with it (deep cycle?) I replaced it with a brand new one. Car started and ran fine. I drove it to school the next day, then home and ran some misc. errands. On the way home from a baseball game at about 10 pm she suddenly up and died again. At this point I was thinking alternator, so it was towed to a nearby Jensen tire, filled out a deposit form and in the morning they called and said it started up fine for them and that it wasn't the alternator and could be a connection with the alternator. They had it towed to the local mitsu dealership anyways. The dealership said about the same thing but that I needed a new Idle sensor, and replaced the one I had ($300 WTF ). Now comes the tricky part, I have had a datalogger cable hooked up to the car even when not in use, and when it was left at Jensen Tire, I removed it. I thought maybe the logger was draining my juice. So today with the logger removed I drove to school, work and some errands. About the same time of night, she suddenly lost power like before, the lights in the car dim, and my blinkers stop working. The car will kinda lurch like its loosing power in anything about 3k rpm. Its getting to be a real problem, and I am completly lost, it still seems to me it could be the alternator, judging by the way the lights in my car slowly dim and simple things like window motors run slower. The shops said it isnt tho...
Thanks in advance!

 

[91dsmtalon]

Anybody?

 

[madaba]

how old is the battery? might want to take it out and have it tested

 

[steve]

First thing you should check is if the alternator is charging the battery. Hook a voltmeter up to the battery and make sure your seeing greater than 13v and less than 15v when the engine is running. If the voltage is 12.5 or less check the 80A alternator fuse bolted into the engine compartment fuse box.

You should also check your ECU for signs of capacitor leakage. If you find original capacitors have them changed even if you don't see any leakage. The sooner they're replaced the better.

Steve

 

[91dsmtalon]

The battery is brand spanking new, changed it out before started driving it daily, the guy we bought it from says he rebuilt the ECU, trying to put in a new alternator tonight. I bought a volt gauge and installed it, when the car is running it starts up at about 11-12v and slowly goes until 8v than dies...

 

[steve]

If the fuse is gone the alternator could be fine. You should check it first.

Hopefully that "rebuilt" ECU will be ok. Most of the one's I've seen leave quite a bit to be desired.

Steve