My car is having problems accelarating and shifting gears. I took it to my mechanic and he told me I needed a major tune up. I have that done. They also recommended that I change out the coolant, which I have just completed. i also ran a bottle of fuel cleaner through the system on my last fill up. It stopped the shaking while I'm stopped at a red light, but it still doesn't accelarate very well and it seems like it's not shifting gears properly. The check engine light is also back on.