PCM/ECU Options?

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DaJeff
Posts: 4
Joined: March 24th, 2022, 6:15 pm
Vehicle Year: 1983
Vehicle Make: AMC
Vehicle Model: CJ7

PCM/ECU Options?

Post by DaJeff »

First post on the forum. I've been a lurker here without an account reading up on small things here and there but looks like its finally time to dive in.

So first off, I have a 1983 Jeep CJ7 that I swapped a 4.0 into from a manual trans 94 Cherokee. I even kept the fuel rail on it for MPI. I gutted the factory engine harness down to the bare bones basics (the Cherokee harness has a lot of "fat" on it) and spliced it into the Painless harness on the CJ7 (I redid the entire electrical system on the Jeep previously). After some tinkering I got it to fire up.

So here's the kicker. I intend to turn this thing into a 4.7 stroker. Step one was getting the 4.0 into the CJ to make sure the wiring was good to go and that it would actually run (when parked lol). I did this knowing I would eventually end up pulling it back out anyway. While the 4.0 was on the stand, I did a couple bolt on upgrades to the engine since I am planning on stroking it in the future. 24 lb injectors, after market aluminum fuel rail, bigger throttle body, and Banks Headers (which go to the custom 2.5 in exhaust). The CJ also has an in the tank fuel pump with 3/8 line going to the fuel rail.

Currently I have the stock 94 manual trans Cherokee PCM running the engine. I have zero knowledge when it comes to tuning (I am made of pure big chimp energy. I hit thing with hammer), but I have a buddy who cant help but tune everything to 1000 HP. So you could say I have someone who can handle the tuning side of things.

Now for the actual questions?

Will the stock PCM run the 4.0 in its current modified configuration?
Will the stock PCM run the 4.0 when its stroked to 4.7?
What are my options as far as after market ECUs/PCMs and what would I need to do to the engine/wire harness to use them (again, I have someone who can tune it to hell and back so that wont be a problem.)
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Cheromaniac
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Re: PCM/ECU Options?

Post by Cheromaniac »

I ran the stock PCM in my '92 XJ both when I had a modified 4.0 and when I did the 4.6 stroker conversion. In both configurations it had Ford 24lb injectors and I used my homebrew MAP adjuster to dial in the air:fuel ratio.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
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275/350 I-6
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Re: PCM/ECU Options?

Post by 275/350 I-6 »

I built a 4.0/4.7 engine using parts from Russ Pottenger. I started with a 1993 block, and a 1996 0630 head, and a late horse shoe intake, and a banks header, with 2.5” hi flow cat & muffler. Over boring the block .060” and a 258 crankshaft gave me 284 CI.

I run the 1995 OBD-I ECM, PCM and engine wiring harness with 24 lb injectors.

Compared to the 258 it replaced, I more than doubled the power. My engine runs like a champ, and this Jeep is fun to drive.

I have never heard of an aftermarket ECM for this application, however; if you run the newer OBD-II harness, ECM & PCM you can tune it, unlike the OBD-I.
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DaJeff
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Joined: March 24th, 2022, 6:15 pm
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Re: PCM/ECU Options?

Post by DaJeff »

Cheromaniac wrote: March 25th, 2022, 12:23 am I ran the stock PCM in my '92 XJ both when I had a modified 4.0 and when I did the 4.6 stroker conversion. In both configurations it had Ford 24lb injectors and I used my homebrew MAP adjuster to dial in the air:fuel ratio.
Homebrew MAP adjuster? How did you go about making that just out of pure curiosity?
DaJeff
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Joined: March 24th, 2022, 6:15 pm
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Re: PCM/ECU Options?

Post by DaJeff »

275/350 I-6 wrote: March 25th, 2022, 8:33 am I built a 4.0/4.7 engine using parts from Russ Pottenger. I started with a 1993 block, and a 1996 0630 head, and a late horse shoe intake, and a banks header, with 2.5” hi flow cat & muffler. Over boring the block .060” and a 258 crankshaft gave me 284 CI.

I run the 1995 OBD-I ECM, PCM and engine wiring harness with 24 lb injectors.

Compared to the 258 it replaced, I more than doubled the power. My engine runs like a champ, and this Jeep is fun to drive.

I have never heard of an aftermarket ECM for this application, however; if you run the newer OBD-II harness, ECM & PCM you can tune it, unlike the OBD-I.
This is very helpful. Seems like I shouldn't have much to worry about other then making sure this 4.0 I swapped in is even good to go. I have only ran it when parked in the CJ and not for very long. Engine and harness came from a junk yard. (engine was stored in doors with oil not drained so I have higher hopes for it overall)
DaJeff
Posts: 4
Joined: March 24th, 2022, 6:15 pm
Vehicle Year: 1983
Vehicle Make: AMC
Vehicle Model: CJ7

Re: PCM/ECU Options?

Post by DaJeff »

275/350 I-6 wrote: March 25th, 2022, 8:33 am I built a 4.0/4.7 engine using parts from Russ Pottenger. I started with a 1993 block, and a 1996 0630 head, and a late horse shoe intake, and a banks header, with 2.5” hi flow cat & muffler. Over boring the block .060” and a 258 crankshaft gave me 284 CI.

I run the 1995 OBD-I ECM, PCM and engine wiring harness with 24 lb injectors.

Compared to the 258 it replaced, I more than doubled the power. My engine runs like a champ, and this Jeep is fun to drive.

I have never heard of an aftermarket ECM for this application, however; if you run the newer OBD-II harness, ECM & PCM you can tune it, unlike the OBD-I.
Also your set up looks amazing. What did you do to mount up the fuse box? I have mine oriented similarly but I took the stock mounting bracket and cut and bent it to bolt into the fender where yours looks like its attached to the battery tray.
275/350 I-6
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Re: PCM/ECU Options?

Post by 275/350 I-6 »

Yup, that’s what I did. My Battery tray is pretty much rust free, I welded a couple strips of angle iron to the under side of both the tray and the bracket that the ECM slides into. I put the ECM on the firewall on the drivers side down low.

These engines are tough, and easy to rebuild. I am pleased with the power and drivability of the new 4.7 engine.
215CFB68-489F-4587-8088-D69CE54F2779.png
313A87D3-9D22-4B47-A231-EFFCB30A5CA5.png
E6598063-AFFA-4746-8981-05A17727E563.png
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Cheromaniac
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Re: PCM/ECU Options?

Post by Cheromaniac »

DaJeff wrote: March 25th, 2022, 12:11 pm Homebrew MAP adjuster? How did you go about making that just out of pure curiosity?
Here ya go:

https://www.angelfire.com/my/fan/MAP_adjuster.html
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
275/350 I-6
Making Progress
Making Progress
Posts: 75
Joined: February 4th, 2020, 8:48 pm
Stroker Displacement: 4.7
Vehicle Year: 1985
Vehicle Make: AMC
Vehicle Model: CJ-7
Location: NC

Re: PCM/ECU Options?

Post by 275/350 I-6 »

275/350 I-6 wrote: March 25th, 2022, 12:48 pm Yup, that’s what I did. My Battery tray is pretty much rust free, I welded a couple strips of angle iron to the under side of both the tray and the bracket that the PCM slides into. I put the ECM on the firewall on the drivers side down low.

These engines are tough, and easy to rebuild. I am pleased with the power and drivability of the new 4.7 engine.

215CFB68-489F-4587-8088-D69CE54F2779.png

313A87D3-9D22-4B47-A231-EFFCB30A5CA5.png

E6598063-AFFA-4746-8981-05A17727E563.png
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darkcorp
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Re: PCM/ECU Options?

Post by darkcorp »

There are some concerns about the adjustable MAP as Jeep ECU checks MAP's voltage before the start up and takes its value as a base point. Although you don't change the voltage after the start up.
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