It's time to diagnose the problem or take it to a shop that will perform the diagnosis. These are difficult problems to solve, and almost impossible without physically experiencing the problem and performing diagnostic tests while the vehicle is acting up.
I have a 1998 Montero Sport. I'm assuming you have over 75K miles on yours? This happened to me also, right around 75K miles. Luckily, I have a good garage that I go to and they knew exactly what the problem was. Mitsubishi placed 'special' spark plugs in the truck to start going bad at around 75K. (Wasn't that nice of them!) Once I had them replaced, it corrected the problem and I haven't had a problem since. That was about 4-5 years ago now. It cost about $450.00 because of the labor to get to the plugs, but was well worth it.
i have a 2002 montero and i had the same problem off and on,computer gave no codes so they took a shot in the dark by taking apart the throttle body,sure enough it was horrible,cleaned it and that was all she wrote...
My son left lights on and drained battery of 2000 Mitsubishi Montero Sport (3.0)
He must have reversed leads initially when he went to charge battery. This must be common scenario that may burn open the 100 amp fuse link and burns out the Fuel Consumption Unit, Mits part# MR239764.
Car goes into rough stall after warming up. For detailed people, when the car goes into closed loop after hitting certain temp (150F I believe) the computer calls for fuel increase (~25%) since car goes lean but no reponse from car. Checked out many things but couldn't ID problem.
Saw similar symptoms on a website thankfully and replaced Fuel Consumption unit. Fixed the problem.
Part is located inside car behind right most panel cover near passenger's feet. 2 plastic black "screws" hold it in place. Fuel Consumption Unit has chrome/silver cover.
1st clue was this part was very hot to the touch. Next to several wires so it didn't make sense why it could run so hot. Looked it up on internet and ran into this site. Best thing I did.
Relacement part did not run hot, warm at best.
One last thing, dealer wanted $260+ for replacement part but we went to nearby junk yard and picked up used part for $2.20! Part is same for several year models 1997+ apparently.
have had the same problem, with my 1998 montero. had the injectors cleaned and throttle cleaned. cleared right up. i add some injector cleaner once a month to the fuel tank. really helps it to stay clean.
i personally don't like a lot of hassles with my vehicles.
We just had our 2002 Montero Sport in the shop for antilock brake issues and found the battery was not holding a charge. Turns out the ABS pump was failing and running when not engaged, which was draining the battery.