Mitsubishi Repair: 90 montero, fuel filter, fuel supply

Question
Hello, i have a 90 montero 4x4 3.0 v-6 auto that will start, but when i put it in drive etc it will misfire heavily and stall. It will also heavily misfire when in park and i give it about 1/4th throttle and it will stall or try to stall. It will idle with no problems forever. If it is running and i try to go to 1/2 throttle or more it acts like the fuel was instantly cut off and will stall. Hard to restart.  Thanx for your help!  Tom.

Answer
Tom,
This sounds like a timing problem or maybe a fuel supply problem.  If you have a clogged fuel filter or weak fuel pump, your engine will stumble when you give it gas.  This may be why your idling is fine since very little fuel and air are needed.  You may even have a faulty or clogged fuel injector.  So at least replace your fuel filter and get the injectors and pump inspected.  Also have your ignition timing checked.  If your timing is off or perhaps you have some bad spark plugs, that can also cause this problem.
Good luck!