I changed my timing belt but why does my car not hold idle?

I purchased a used vehicle for about 300$ knowing that I had to fix a timing belt issue. While making the repairs I discovered that the reason the timing belt snapped the first time, was because the seal around the thermostat was seeping and dripping down into the sealed area of the timing belt, causing slippage. After replaceing the timing belt, cleaning the area and replacing the thermostat, the car now runs. However, it does not hold idle and will die off if I do not keep my foot on the accelerator. Yesterday I tried to start the car and it turned once but the battery was low, so after charging it overnight I hooked it back up, and now the car acts as it did before changing the timing belt. It won't turn over and it backfires. Any suggestions?