I've spent the last couple years rebuilding this Sport - replacing all the electronics, sensors, mechanical, new rear ProRock axle, complete tear down of the front and new CM shafts, brake redesign, etc. With 600K on it everything was finally starting to show the wear and tear it gets. But, with the exception of a couple misc things, that looks like its done.

The last engine swap specific thing on my list that we didn't do was changing out the 3.5L injectors for the 3.0L injectors. That was completed today. It was somewhat of a surprise that it started and runs. I only had Internet rumor and some 3G/Eclipse reports to go on, so ....

LT fuel trims with the 3.5L injectors were running in the -2.4 to -4 range all the time and STFTs were all over the board slamming +/- as far as they'd go constantly. Metering was obviously horked because of the mismatch between the programed data in the ECM explaining the 3.0L injectors it THOUGHT were installed and the physical reality of the higher flow 3.5L injectors that were ACTUALLY installed.

As documented earlier, this isn't news. I knew what was going on and could even 'fix' the issue with the AEM FIC - except the #2 injector CEL/OBD problem made this unworkable in an emission test state.

Like I said, the good news is it runs. LTFT low is -0.8 and mid is -1.6 now. STFTs calmed WAY WAY down and are not constantly slamming from one extreme to the other. Except that they are in the negative, FTs now look the same as my stock '97 3.0L and my '03 3.5L. FSMs and the techs say that +/- up to 2.5/2.75 is acceptable. Obviously the closer to zero the better.

The ECM hasn't exhibited any of its random wigging out behavior, either. So far. Everything is nice and stable and steady.

And the slightly rich fuel smell from the exhaust I've had since the day we did the swap has disappeared.

To this point I haven't noticed any change in driveability bad or good other than its glass smooth and purrs like a brand new engine.

Edward

Quick update since I can't edit a #*%@ post.

LTFTs are running -0.8 to -2.3. The latter is after 30+ miles of mostly downhill, otherwise its -1.8. STFTs are back to normal and no more flaky behavior from the ECM.

Almost zero change in driveability. As expected STFTs have shifted +, but its not nearly as bad as the STFTs where when they were constantly shoved as far negative as they'd go and everything appears to be functioning fine.

I can't tell 'cause the weather changed and the temps have dropped 20-30 degrees but power seems to have bumped up just slightly on the highway. Probably my imagination.

I couldn't complain before but it's smooth as glass now - absolutely scary smooth, idle all the way to 6000K RPM.

There is NO smell from the exhaust at all now. I let it idle for 20 minutes this morning while I was messing with the scanner and never got a whiff of any kind of exhaust smell.

I'm going to slap the laptop on it this weekend and take it for a 7-8 hour drive and see how it does on the mountain passes and do a little light wheeling. I'm a little concerned about off road after messing with things this morning because getting rid of the perpetual rich condition may have made the running hot issue worse but I'm not positive. I may have miss-set the bottom on my electric fans - which makes a big difference - or it my be rampant paranoia.

Otherwise, for anyone doing this swap, CHANGE THE INJECTORS. The 3G/Eclipse/etc guys are right. It may STILL not be optimal, but its a hell of a lot better than running the 3.5L injectors on the 3.0L ECM.

Edward

Edward,

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.

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.

Once again, thanks for the info, It's got me very excited about my own project.

-Jeff

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.

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.





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

Thanks to your site, I knew all that going in I got extremely lucky. The truck I pulled the engine from was wrecked, so that means it was drivable before it ended up in the yard. It was also half off weekend, so I got the entire long block (minus the alternator and AC compressor) for $150 out the door. Even if it's ruined, it'll still yield a ton of usable parts.

Someone had also yanked the motor out of a 3.0 Sport, and they just left the motor mounts laying on the ground. I just walked by and picked them up. How convenient is that? One of them is the same exact part as what's on my Max, and the other one is very similar. So now I've got good cores to cut up and use with my 3.5 block plates.

The 99 Montero ECU got here Friday. I haven't dumped the ROM yet. It's MD361885. 3 connectors, no integrated TCU, 3.5L engine. I'm expecting it to be like the 3000GT and Eclipse ECUs where the engine code was the same regardless of whether it was an auto or manual. The only communication between the engine and trans computers was a torque reduction signal and a park/neutral signal. If you leave the torque reduction disconnected and permanently ground the park/neutral line, it's enough to convince the computer it's in an MTX car.

I had actually gotten an integrated PCM to start the engine in my 6 speed Stealth, but I never took it any further than that. It was mostly just to see if it was possible in case we had a hard time getting standalone ECMs. The ECMs ended up being a better option all around, and they were a little easier to come by than we originally thought.

The only other thing is the immobilizer. That can just be disabled. It's been a while since I read up on it, but I think the trick there is to just set the immo code to FFFF. Worse case, I can bypass the immobilizer routines completely with some minor code edits. I've done a ton of work on the 3000GT code, so I'm not expecting any surprises in the truck code.

It'll be a little bit before I can get my plate clear enough to tackle this project in earnest, but when I do I'll post a thread about it.

Nice! You got the motor mount brackets, not the motor mounts themselves, right? It was the brackets that bolt to the frame that the motor mounts themselves go to that I had to chop. Mine still uses the OEM 3.0L motor mounts.



Mmmmmm. I'll have to look that one up. As far as my research has gotten me, and from experience, the code should be largely the same. Only the maps should change. That was my theory behind running the old 3.5L ECM A/T. I just don't have enough visibility into the A/T buss - which I think is where I'm hung up.

It would be interesting to know.



I'm currently working with ECMs, not PCMs. The early Oct '96 1997 Montero Sport is almost identical to the '96 Montero ECM-wise. The very early Gen 1 Sport - which is what both my '97s are - were barely more than rebodied Monteros electrical system-wise.

I have the buss open - since there's nothing to connect it to - and I believe I've tried grounding the park/neutral to no effect. I'll have to look at my last Boomslang harness and see.

I'll take a look at that ECM P/N. Now I'm kind of curious.

Edward

It's been a while, but I finally dumped the ROM off this thing. There's no immobilizer (confirmed by ASA). I'll upload it when I have a basic definition file made.