Jeep Comanche - Renix ECU Upgrade and Sun Visors

Operation MJ - Part 8:
-Sun Visors
-ECU Upgrade
This is a 1987 Jeep Comanche. It is equipped with the AMC 4.0L Engine, Peugeot BA 10/5 5 Speed Manual Transmission, NP231 Transfer Case, Dana 35 Rear Axle and Dana 30 Front Axle. It is the Long Wheelbase configuration with a 7 foot bed. I bought it with 115,000 miles, and in this video series, I planned to restore the truck, but it's kind of become a matter of keeping it alive.
In 1987, the first year of the AMC 4.0, it was rated for 173 Horsepower and 220 Torque. Jeep would later raise these numbers for 1988, despite it being the exact same engine, through the work of refining some internal programming in the Engine Control Unit (ECU).
By 1990, the 4.0 produced 177 Horsepower and 224 Torque. Although not much, it was an upgrade, the extra output a bonus alongside a smoother running engine all around. The cool thing is, these ECUs are interchangeable, so if you have a 1987 or 1988 Jeep Cherokee or Comanche, you can find an ECU from a 1989 or 1990 Jeep Cherokee or Comanche, just plug it in, and get those improvements.
Ideally, you should find one for your combination of engine/ transmission, as there were different ECUs for 2.5s, 4.0s, Automatics, and Manuals. (4wd does not differ). I have absolutely no idea if upgrading the ECU in a 2.5L engine does anything, but the 4.0 ECUs are interchangeable with each other so you can actually put an Automatic ECU in a Manual truck and it will still work.
I was lucky enough to find a 1989 4.0/ 5 Speed ECU for my 1987 4.0/ 5 Speed MJ. It is undoubtedly the best "fix" I have done.
With a 1987 ECU:
-Every cold start, the engine seemed like it had to relearn how to idle, and would sometimes stall.
-Every Warm start, the engine would rev past 2,000 RPM and then slowly settle down, as if I had the accelerator pressed when turning the key.
-Slow transition between shifting gears
-Overall performance relatable to a tractor, producing enough power, but nothing more.
-It had a yellow tag on it, which is my ex's favorite color and is what indisputably caused all these problems.
With a 1989 ECU:
-Cold start resulted in a smooth, non-fluctuating idle that showed no signs of stalling.
-Warm starts, (although having a noticeably longer crank time) do not rev the engine super high, it just kinda starts like a normal car engine.
-Gear transitions are smooth, fast and predictable. This is the best part, and nobody on the internet talks about this. You can shift gears SO MUCH FASTER. It literally feels like a race truck.
-Overall performance relatable to a more refined car, it now drives much more like my XJ (OBD-II) than another '87 Renix.
-It has a blue tag on it, which is the second best color (right behind orange), that matches the truck and is indisputably what caused all these performance upgrades.
I am incredibly impressed with this, I was not expecting really anything aside from a smoother idle, and I would have made a before and after video had I known it would be so divisive. There are videos out there with before and after dyno tests and the computer really does change how the engine runs.
Renix ECUs seem to average about $100 nowadays, I got mine for about $55 so I had to jump on it. This isn't something I really "wanted" to do, I just figured I "might do it someday, I dunno" and well, now someday is today. Very glad I did this though, the truck no longer feels underpowered.
Apparently you can buy a new ECU from here, I don't know how trustworthy they are but I found that interesting: www.rockauto.c...