How long have ou been driving it? I usally put some into the fuel every 3 or so oil changes and I have no problems. The only time I had a problem with this stuff is when I put it into the vacuum line. It stumbled and backfired a lot, but only for like 20 miles, then it was back to being it's old self. If you put it into the fuel I would go through another tank of gas, and then change the fuel filter.