Mitsubishi Repair: Vibration and a CEL, crankshaft position sensor, mitsubishi eclipse

Question
I just bought a 1993 automatic mitsubishi Eclipse 3 door hatchback with a 1.8 engine. About a week ago i let my sister take my car to her friends house. Five minutes later she called me saying she couldn't get it to start. I go over there and finally got it to start, but it died a minute or so later. We finally got the car started and home. For the next few days the car wouldn't start and the engine wasn't turning over. Well, now it's starting, but it has a very bad vibration, rough idle, and sounds horrible. Before it was as smooth as could be. It has new spark plugs and wires and the battery is good. The starter needs to be replaced, but i don't think that is the problem. I checked out the air filter and it seems fine. When i bought the car i did notice that there was a half of a quart extra oil. I haven't drained it out, but plan on doing that today. Could that be the problem or is it a sensor? Thanks for your help.

Answer
Christina,
You should have your car's timing checked.  If your timing belt has skipped a tooth, or if your balance belt broke, you will experience very rough vibrations and poor idling.  Your CEL may come on because your crankshaft position sensor detected that your timing is signifigantly off.  Have a mechanic check the timing belt and replace it if necessary.

Another thing that should be checked is your car's computer.  Read this article for further information:
http://www.90gsx.com/eclipse/cap/caps.htm

If your ECU is damaged, you'll have all sorts of starting and idling problems.  Have it checked for possible damage.
Good luck!