That was my problem. I feel like a retard... I was running an autocross setup with less fuel for weight (does the game even factor this in?) and I forgot to change it when I went to track the car.
Ok, I purchased LFS over a year ago and have been playing with no problems until a few days ago. Now, every time I try to do a lap in Single Player, the car shuts off after the first checkpoint on every race. In Hot Lap mode, the same thing happens, but it seems to be about halfway through the lap.
As soon as I cross the first checkpoint, the accelerator stops responding, and the car coasts to a stop. Brakes, steering, and shifter work fine still, but I can't accelerate. I know it's not a hardware/wheel problem, since everything works fine until I hit the first checkpoint.
I did a search for this and found nothing. Is there some option I set accidentally that will cause this? Or do I have to reinstall to fix this?