Hi! Please help!! I have a problem with my 2008 Impala 3.5 flexfuel., 310 000km. If I slowly accelerate, everything is fine. But when I put the gas pedal more than halfway down, the engine stutters and hesitate. Also when I decelerate and I want to accelerate, the engine stutters at 1000-1200rpm, and I need to release the gas pedal and try to push it back very slowly to accelerate. The code P0300 (randomly misfire) is active and when the engine hesitates, the check engine light flashes during 30 seconds. The plugs are ok (40 000km but I took two out of the head and they are good) the wires are also ok (changed a couple of months ago) I also changed the coilpack, the throttle pedal and the throttle body....but didnt fixed the issue.. When I changed the throttle body, Ive seen that there is a lot of sludge stucked on the "walls" into the intake manifold. The car was a taxi before I bought it. It was 240 000km, but Im not really sure it was the real milleage, (and what about the idle hours!!) so I think it might be really dirty in the engine. I bought a seafom can to put in the fuel tank to clean the injectors, and to clean the interior of the engine. Does someone already had the same problem or know what I could try to fix it? I do not have a lot of money to bring the car to a mecanic and I really love this car. I drive a little more than 100 km a week. Thank you for your help guys, and girls !!