Mitsubishi Repair: 1993 Mitsubishi Expo, air fuel ratio, spark plug wires

Question
I recently purchased a 1993 Misubishi Expo with 108,000 miles on it. The engine is the transverse 4 cylinder. I have had the engine tuned, etc. The engine stumbles at idle and will sometimes even die at stop lights. The CEL is not on. At highway speeds the car jerks and stumbles through acceleration, until I'm driving 70 to 80 mph, when it levels out and stops stumbling. While accelerating onto the freeway from on ramps or from stop lights the car jerks and stumbles.
   I have taken it to 2 mechanics who could not duplicate the problem in the shop. One mechanic said the problem may be with the distributor shaft, (worn) and that the distributor assembly may have to be changed to fix the problem. But basically, no one knows. Can you give me some clues? I would appreciate it.



Thanks for your time.


Sincerely,


Lance Veit
Davis, California

Answer
This could be as simple as a gas problem...sounds like your missfiring, but small enough to feel the difference but not consistant enough to set off engine lights! But the distributor/ignition wires would be a good thing to check.. if your having missfiring and the distributor hasnt been changed in a while...CHANGE IT OUT! You could probably do it yourself.. They are cheap at AUTO ZONE!!!!..check your spark on all spark plug wires, wiring harness that leads to distributor, spark plugs,air filter....as far as the missfire..you missfire when the air/fuel ratio is unbalanced so if you have a clogged injector or fuel filter, or pump, it would cause some jerking, then level out when air/fuel is balanced..try running some LUCAS INJECTOR cleaner from Auto Zone...Mechanics cant duplicate because its a driving/spark problem...Keep troubleshooting little things before taking it to mechanic! Follow up with me if need be...


Good Luck!