car wont start v. 2

[jd1828]

Its doing it again! Its a stock 96 tsi awd. Im back in Duluth and it was around -10 last night. I just went out to start my car. It turns over but kind of slow. It should be enough to start the car though. The problem is that it fouls the plugs. The car will sputter and try to start but never does. Last time this happened I had to change the plugs out and it started right up. Any ideas why this keeps happening. Im thinking that the battery is going bad even though my tester says its good.