Mitsubishi Repair: mitsubishi lancer 1993 surging, mitsubishi lancer 1993, vacuum leak

Question
Hi I am from australia with a 1993 cc lancer coupe with the 1.5L carby. I have an intermittent problem that around 2800rpm the engine will surge violently thus jerking the car back and forth. When this happens, i can put it in neutral and hold the throttle constant at this point and the engine will rev up and down for a bit then finally returns to normal revving. It seems to happen when the car is hot or cold, but I think if I warm up the car before going for a drive it doesn't happen.
Any suggestions would be great I have been to some mechanics and a dealer but they either couldn't reproduce the problem or didn't know what to do.

Answer
Jarrod,
I have little experience with the older Lancers, and no experience with a carborator one.  But from what I do know, this sounds like a fuel/air problem.  It could be a failing fuel pump, clogged fuel filter, clogged air filter, or perhaps a vacuum leak somewhere.  Your carb may just need to be tuned, and your timing should be checked.  I'm not sure what functions your car's computer monitors and regulates, but that should be inspected to be sure the computer is not malfunctioning.  Check those areas and maybe you'll find the problem.  Sorry I couldn't be more help.
Good luck!