Dear Doctor: I own a 1997 Dodge Stratus with 225,000 miles. I have a bucking problem with the car. When driving say 65 mph, and lightly letting off the gas pedal, and then lightly applying gas again to maintain speed, the car starts to buck. It shows no codes. I have replaced the throttle positioner, cam sensor, wires, plugs, PVC, fuel filter, a hose to the PVC valve, and had the throttle body cleaned. Can you help? Bob
Dear Bob: Very likely the EGR valve is not closing 100 percent when decelerating on the highway. If the EGR valve does not close 100 percent, then as you lightly step on the gas pedal the engine runs lean, which causes the bucking. Another possibility is the engine timing is too far advanced, either by the computer, timing chain or timing belt slack. Have the technician bypass the EGR valve for testing purposes to start with. This problem usually only happens in high gear with manual transmission vehicles. Unlike automatic transmission vehicles, there is no transmission slippage with manual transmission vehicles.