Mitsubishi Repair: 92 eclipse 1.8l manual, stepper motor, drive belts

Question
I have a 92 eclipse 1.8l manual
while driving the car the car started to jerk vigorusly then the engine started to loose power and finnaly cut of I took it to my father and we changed the fuel filter, oil filter, and air filter. but the problem persist he thought it may be the fuel pump that was causeing thee the problem so we took it to one of our mechanic friends to put on the fuel pump. he told us that it was not the fuel pump that was giving the problem. he says it may be one of the sensor that are bad. now when you turn on the car it strains at idle and sometimes looses power and shuts off at idle. also when you step on the gas sometimes while in nuetral it will shut off. and when the car does idle good as soon as you put it in gear it starts to act up. it will strain and jerk past 2500-3000 rpm  then rum ok at 4-5000 rpm then as soon as the engine gets warmed up it will start to loose power even when you step all the way down on the gas pedal. Can you please give me an idea of what may be the problem .

thank you  

Answer
Shaun,
The first thing you should try is a good old fashion tune-up. If you haven't had one in the last 30,000 miles, now would be a good time. Replace your spark plugs, plug wires, distributor cap, distributor rotor, and PCV valve. Check your drive belts and have those replaced if they look worn. Your timing belt and accessories should be replaced every 60,000 miles.

Also try adding a bottle of fuel injector cleaner along with a full tank of premium gas to see if that helps. You may also want to have your Idle Air Control (IAC) motor inspected to see if it's working properly. This little stepper motor mounted under your throttle body can go bad over time and cause what is known as 'Idle Surge', which is very similar to what you are describing as the problem with your car. You can do an internet search for Idle Surge for more information.

I would also have your car's computer checked out. Read this article for more information:
http://www.90gsx.com/eclipse/cap/caps.htm

A bad ECU can cause sputtering and stalling, so it can't hurt to check it out.
Good luck!