the car starts easily and idles smoothly but when I try to drive it it surges and fades as though the fuel pressure is varying wildly.
The check engine light said it was the EGR valve. I replaced that and the fuel filter but neither made a difference. Also, the pressure regulator on the fuel injector rail was replace less than two years ago. help!
put a fuel pressure gauge on it and rev the engine to see if it is the fuel pump.
You can try some techron to clean the injectors.
If the fuel pressure is ok then perhaps the throttle position sensor has a problem.