Mitsubishi Repair: 90 eclipse jerky acceleration, stepper motor, drive belts

Question
Hello I have a 1990 2.0L Non-Turbo Eclipse and when I try to accelerating from a stop it will jerk like you were pumping the gas and then start to drive fine but will do it again when you get on the gas alittle, also when at idle it will bounce between 1200 to 1500 rpms then drop down to 800 to 900 rpms and stay there. I was wondering what could be some the causes of these problems

Answer
Chris,
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, air filter, fuel filter, 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!