My car started acting up by making a really loud squeaking noise, this was fixed after I added a new belt tensioner. Ever since i've had the car the service engine soon light has been on constantly. Recently it started flashing when I would accelerate, but now it's been flashing constantly. My Saturn now shakes at stops, for a while I couldn't stand it, but a can of seafoam in the gas helped temporarily fix this. Gas mileage has been terrible due to the engine problem, I used to get around 40 mpg, now I'm getting less than 30. Finally I brought my Saturn to a mechanic. After running some tests he found out that the exhaust valve on the 3rd cylinder is shot. That wasn't what I was hoping to hear. My only options are to get a new engine or rebuild this one. I think I'll get a new car.