We're trying to track down a strange surging / jerking on my 5 speed 93 wagon. In the past few months we have cleaned the air idle valve and replaced the fuel pressure regulator. Prior to that the car has new fuel sender and both fuel pumps have been replaced as well as the filters. The problem presents itself randomly and and is most noticeable at highway speeds. The car will drive fine and then you will get a weird surge/jerk and then it will stop and start intermittently continuing until you stop and let the car rest. Sometimes the problem reoccurred upon restart sometimes not.
I ran down the fuel to empty, added a can of Lubromoly Jectron cleaner and the problem has essentially stopped but still occurs in rare for short bursts. Are we missing anything? Any thoughts would be appreciated.