Mitsubishi Repair: ECU, fuel injector, compatability issues, eclipse gs

Question
Hi i have a 91 eclipse gs 1.8 automatic and im having a problem with one injector. My cousin rebuilt the engine for me and told me that he had replaced the ECu twice becuase it keep messing up the same injector. Im not sure if its the injector thats bad or the ECU. The car keeps losing power and it seem like it runs on 3 cyclinders. What do u think can keep breaking the ECU.

Answer
Carlos,
The ECU you are using should match exactly to the original.  Some folks will tell you that an ECU from a 2.0L Eclipse, or an ECU from a manual 1.8L Eclipse will work, but you will have compatability issues.  Another problem that could be happening with the ECU is that the capacitors on the ECU board may have leaked on the to circuit board and ruined it.  That is a very common problem with older Eclipse.  You can read this article for more information:
http://90gsx.com/eclipse/cap/caps.htm

If the ECU is bad, you'll get all sorts of strange problems.  The most common one is the inability to start.  But to just have a single injector not fire is a bit odd; even if the ECU was bad.  There might be a bent pin in the ECU harness or a fraid wire leading from the harness to the injector; shorting it out.  Check all the wiring leading from the fuel injectors to the ECU.  Odds are you might find your problem there.  Switch the non-firing injector with one you know is working.  If there is a wiring/electrical problem, then the previously working injector will not function when switched.
Good luck!