My 2005 Saturn Ion has been giving me trouble the past couple days. After the car is warmed up, when starting to move from a stop, around 2000 RPM the car start bucking and chugging. Often while it's bucking the check engine soon light flashes. However, once I get out of first gear, it usually evens out and runs perfectly with it occasionally giving me issues in 2nd at the start. I can help minimize the issue by going very easy on the throttle through 1st. I also get codes P0326 (knock sensor), P0121 (TPS sensor), P0300 (random misfire) and a couple other codes I didn't write down. When searching for others with these symptoms, people often say that the coils and ignition module need to be changed together, so I did. I also changed the fuel filter since it was original to the car with 240K on it. Neither of these changes helped. I changed the spark plugs 3-4k miles ago. I know your first impression would be to say the transmission is slipping in first and that it's going out, but would it cause the engine to start missing and jumping around like crazy until I got out the gear? The check engine light flashing is the universal indicator of a misfire, which is exactly what happens when this occurs. Any ideas? This is my commuter car and I need to get it back into operation ASAP. - - - Updated - - - A couple more thoughts: No matter how hard I step on the accelerator, including putting it on the floor has no effect on the RPMs when it's happening. The acceleration when it does this is also dead slow.