I wanted to thank you for the extensive information you've shared. I realize it won't be a 1 to 1 swap, but your page has given me a lot of insight into what I'll need to drop a 6G74 (or 75) into my 92 Mighty Max 4x4. Based on what I've dug out of ASA, a lot of parts on my old truck were common to the 3.0 Montero Sport. So going forward to a 74 should be fairly straightforward. I picked up a fair condition 6G74 at the junkyard last weekend. Things are looking good so far.
The two notable things that are different are the plate that fits between the block and bell housing and the engine mount pedestals. As long as you get a complete 3.5L, including accessory brackets, manifold, etc. its pretty easy 'cause, as you've found out, almost everything is the same between the 3.0/3.5L.
OH, and you may need to make your own throttle cable bracket.
I apologize if I missed this earlier, but I was wondering why you haven't swapped over to a 98-99 ECM-only flash ECU and then wrote the tables from the 3.5 ROM to it? I've been heavily involved with 3000GTs for a long time, and we've been swapping ECUs between different models (Eclipse, Diamante, 3000GT, Montero Sport) for a while.
Turns out the 98-00 3.5L full size Montero has a standalone ECM. No integrated trans controller. A lot of other Mitsus went to an integrated PCM in 99. I guess the Monte didn't get it because they were doing a full redesign on the truck around then.
I've got one on order for my project. Same injectors and MAF between the 3.5 Sport and the 3.5 full size. Should be plug and play once I build a harness and flash the immo out of it.
Believe me, its not for lack of trying! The '96 Montero and '97-99 Sport ECM isn't programmable. The '99 PCM is. I have ECMs from '96 through '99 and two '99 PCMs. No matter what I do, I can't even get the vehicle to start and run. There are wiring and sensor changes throughout the years and I have a 5-speed M/T - all the 3.5L ECMs are A/T. So, I'm still missing something - I suspect its the missing TCU. The '96, '97-'99 2.4L and 3.0L have separate TCUs from the ECM. Unfortunately, I don't have a TCU and harness to try my theory.
Hopefully you have better luck. I haven't had the time to dedicate to figuring out the ECM programming/flashing/whatever any further than I've gotten. To be honest, at this point I'd rather put a MS on it in piggyback mode.
Let me know how it goes. The 3.0L timing really is too much for the 3.5L and its starting to show. Little by little the fuel mileage is eaking down. Still runs like a top and smooth as glass, but I'm guessing if I do a compression test I'll find its down and slowly sinking.
The 3.0L injector swap is FANTASTIC. I haven't had so much as a hic cup out of the ECM, still smells clean and the power did edge up just a bit. Under some conditions it does run JUST a TAD warmer - like 3-4F degrees - but its brief and seldom. Just enough to notice but not enough to make any difference.
I'm moving on to the '99 build now. The injectors were the last thing pending with the actual swap. Unless something changes, I'll run it as it is until the 3.5L needs replaced. Or I get really bored.
Keep us posted and let me know how the ECM flashing thing goes!
Edward
