TJ de-computerization help

[NskLJ]

The computer doesn't control the heat, the coolant flows to the heater core at all times (so long as the thermostat is open, I guess?), but the fan & vents don't route through the computer.

OP, I support you in your efforts to de-computerize. The long-term availability of the computer is something that worries me, but I'm probably old enough that I'm not going to have to really worry about it. Anything is possible, so I'm sure converting your 4.0L to carb fed can be done. But to make it something you can do on your own you're going to need to understand everything that the computer controls. First and foremost in my mind is ignition. Your timing is set by the computer, so you'll need to find a distributor that will fit a 4.0 but has a mechanical or vacuum advance and allows for the initial timing to be adjusted by hand. Next is fuel delivery, because honestly I don't really know how the fuel delivery works in our TJs, but all I can think about is how every carb'd car I've had also had a mechanical fuel pump mounted on the block, which you won't have.

The gauges won't be that hard, you can run aftermarket oil pressure, water temp, and voltmeter for sure. Fuel level might be a trick, I'm not sure what magic the computer performs on it before it gets to the gauge, but maybe nothing? Or maybe there is a known ohm range for our fuel sender and a specific fuel gauge might work, idk. Speedo can be run directly off the existing sender & the tach can be fed from the #1 spark plug wire. The A/C could be tricky, since the high & low pressure sensors tell the compressor when to kick on/off. You're going to be doing a bunch of custom wiring no matter what.

Your 42RLE transmission probably has to go, it's computer controlled. But you said you wanted a stick anyway so problem solved.

Dropping in a 350 & matching trans is easier insofar as it's already prep'd for being carb fed & lo-fi ignition/timing, but you introduce new problems like motor mount locations, transmission mounts, rear driveshaft length & pinion angles and probably a mess of other things. Oh, and the 350 typically requires a different radiator because of how the hoses lay out. You need one with the inlet/outlet on opposite sides from where they are on the TJ. But that road is well-traveled so you will be able to find a bunch of resources to help you there. And probably a thousand other things.

The availability of the computer it one thing, have you tried to get a decent carburetor or rebuild kit lately? New carb would be the way to go. Fuel pump remove assembly from tank fit a low pressure pump to existing assembly, buy fuel gauge to match factory sender values. A/c is no problem. I think you could just attach the a/c input wire to the A/C on wire together at the computer. May need a relay.

 

[Zorba]

These PCMs really aren’t much more complex than an Arduino in terms of computing. I wouldn’t be surprised if the average hobbyist 3D printer has a more powerful computer than these cars do.

With a bit of careful programming (who does that anymore?), it could probably be done with a 4MHZ Z-80! Z-80s, and Arduinos both are cheap, but they're not by the time they get put into an automobile.

 

[Rickyd]

The availability of the computer it one thing, have you tried to get a decent carburetor or rebuild kit lately? New carb would be the way to go. Fuel pump remove assembly from tank fit a low pressure pump to existing assembly, buy fuel gauge to match factory sender values. A/c is no problem. I think you could just attach the a/c input wire to the A/C on wire together at the computer. May need a relay.

I've been going through carburetor woes on a yj recently. Thinking about either a motorcraft 2100 of even 4.0l injection as a solution

 

[Zorba]

I've been going through carburetor woes on a yj recently. Thinking about either a motorcraft 2100 of even 4.0l injection as a solution

Naw, replace it with a hot bulb setup.

 

[Weasellee]

This is just like all the manual transmission monkeys saying they prefer the manual because they want to control the vehicle. They are just as infatuated with a myth as you are. You are not running the car, you simply driving it after all the things you have no actual control over are doing their job.

If you really wanted to get closer to running the car, you have to go way back to when you had to adjust the spark control on the dash with a cable for adjusting the air/fuel mix on the carb.

Had a ‘48 Panhead with spark/timing adjustments on the handlebars

 

[Weasellee]

If you can't fix it with a hammer, its obviously an electrical problem.

And if the Electrician can’t fix it tear it down and start over. Electricians can fix anything

 

[mrblaine]

you dont buy a saw and expect the functionality of a hammer.

I don't know if that is entirely true. I'm pretty fond of a few computerized tools. There is something to be said for grinders that add speed to the grinding wheel as you load them harder.

Modern day cashiers would file for repetitive stress injuries and lots of time off if they had to operate one of those old manual cash registers for more than a day.

 

[srimes]

V8 in a CJ5 or CJ7 is my plan since the mods id be doing to the TJ would essentially CJ-ifying it. (I had this idea before Jscherb made it cool, and did a lot of hard work to make a CJ-TJ hybrid better than I ever could lol) things like a sport roll bar, flat steel bumpers, downward folding tailgate, and a bunch of other stuff that comes standard on CJs. I found a fair priced CJ5 with a 350 swapped into it and a muncie m20 4 speed transmission. its bright orange too which is awesome.

Carbs are great in many applications, but I quickly learned how they suck off-road. The TJ has a lot going for it over the CJs. The frame and suspension in particular. If you want a linked suspension and will be happy with nearly-stock, I think it'd be easier to put a carbed 350 in a TJ than to put links on a CJ. But if you're sticking with leafs or wanting custom links then a CJ (or YJ!) makes sense.

 

[mrblaine]

2) Anybody who says you don't have better control with a manual obviously doesn't know how to drive one.

I say it, I've said it, and anybody that wants to play hard can be easily shown the difference. You have control of the transmission, I have complete control of what the vehicle is doing when I want it to do it. Anyone who says otherwise has never played hard where it matters. I can do stuff with the rig with an auto in it that you'll watch and go, "alright, fuck that, I'm not even gonna try".

 

[mrblaine]

Carbs are great in many applications, but I quickly learned how they suck off-road. The TJ has a lot going for it over the CJs. The frame and suspension in particular. If you want a linked suspension and will be happy with nearly-stock, I think it'd be easier to put a carbed 350 in a TJ than to put links on a CJ. But if you're sticking with leafs or wanting custom links then a CJ (or YJ!) makes sense.

The big problem with linking those two if you want pretty good travel is they have considerable less wheel arch in the frame than the TJ does.

 

[Woodrow]

You know, I avoided jumping into this thread earlier in the week because it looked like it would devolve into a shouting match pretty quickly. But there has actually been interesting and detailed discussion of the many issues which would come up with attempting to remove a TJ computer or even putting coilovers on a CJ. Also, I credit OP for hanging in with it all. Personally, I'll keep my fuel injected TJ. But good talk!

 

[AndyA]

it could probably be done with a 4MHZ Z-80! Z-80s, and Arduinos both are cheap, but they're not by the time they get put into an automobile.

Z80 was recently EOLed. It's had a good run. Andy

 

[jjvw]

....

I simply just dont like computers running my car. I want to run the car.
its a lost art and a lost freedom, everyone wants everything to be so easy and automated and soulless. On smaller things its fine, and it can be a great convenience, but on the big things that we interact with everyday on a huge scale that are a huge part of our lives it destroys the choice of ours to control and run our own machines exactly how we need, and use our own stuff the way we want to. same principle with modern built houses that aren't the top 1% of homes designed by architects who know how to make a building an art piece or something simple and nice. all of the construction is shit and has no beauty.

....

...
I just dont believe the place for computers to be is in cars or things like self checkout or things like your fridge. each of these things have a sole purpose, certain cars, especially utilitarian cars like trucks and SUVs should be utilitarian cars with no frills and they should serve their purpose and only serve their purpose. you dont buy a saw and expect the functionality of a hammer.

You are a weird person with weird rules.

 

[Rickyd]

Naw, replace it with a hot bulb setup.

What?

 

[ColoJeep]

What?

Antique diesel , or stationary natural gas engine ignition enhancer.

 

[Zorba]

I say it, I've said it, and anybody that wants to play hard can be easily shown the difference. You have control of the transmission, I have complete control of what the vehicle is doing when I want it to do it. Anyone who says otherwise has never played hard where it matters. I can do stuff with the rig with an auto in it that you'll watch and go, "alright, fuck that, I'm not even gonna try".

As long as the autobox can select all gears I'll agree from a practical standpoint. You still can't upshift an autobox until it gives you permission, but 99.999% of the time with 99.999% of the setups out there, you wouldn't want to anyway. I still don't really see the point of an autobox, but it *can* overcome or at least hide lacking in the gearing dept.

 

[Zorba]

Antique diesel , or stationary natural gas engine ignition enhancer.

Yup - yootoob "hot bulb engine" for some interesting shit!

 

[Rickyd]

Antique diesel , or stationary natural gas engine ignition enhancer.

Ha! No wonder googling "yj hot bulb" came up with bupkis

 

[burtpenguinnn]

Clearly you've never been on a construction crew either. Everything is a hammer.

or some sort of adhesive lol

seriously you'd be surprised what i've used as adhesive in various projects, one such example being kraft american cheese singles to hold a speaker on my bike (with the help of some aluminum tubing and friction fitting)

 

[burtpenguinnn]

On a more serious note, have you considered messing with a tuner on your existing PCM? You have a lot more options to control things than you might think. You can change or disable different control strategies, tune it for more power and/or longer range, and realistically you have way better control over it than you would a carburetor or distributor.

Might not be the de-computerization that you are looking for, but it certainly will give you the sense that you are in control. Granted, you could easily destroy your engine by messing things up, but as long as you understand the fundamentals of fuel/air, spark advance/timing, and basic mechanics of engines, it will be very easy to learn. Any person who has messed with a distributor knows it’s probably not a good idea to demand 50 degrees of spark advance at idle even if they haven’t touched a tuner before.

These PCMs really aren’t much more complex than an Arduino in terms of computing. I wouldn’t be surprised if the average hobbyist 3D printer has a more powerful computer than these cars do.

if all my plans don't work out it's certainly something i'll consider and most likely end up doing

for reference, the plan is im buying a cj
I found a CJ5 with a 350 and muncie m20 transmission that I like a lot, it's just a simple cj5 with that swap and a simple lift and bikini top. which is really nice.

if i keep the TJ a transmission swap and pcm tuning is what i'll do (gotta remove SKIM to make the transmission swap not a pain in the ass)