If you have a misfire, or (m)any other electrical malfunctions, especially ignition/fuel issues, that should set a fault code because your emissions should go out of range. Does the "service engine soon" light come on when you turn the key to on but prior to engine crank? If it does not, the light could be burned out and there may well be fault codes set.
It's tough diagnosing these type of issues from a remote location. It's always a good idea to confirm no fault codes are set prior to doing anything else. Lots if retail non dealer auto parts stores will scan your ECU for free if you cant find the plug. Good luck.
Chum lee
