91 Comanche Project

[barimpact]

Hey everyone, I've finally got some progress on my Comanche and since I've gotten a lot of info from this site and should be doing some pretty unique things to the truck, I've decided to start a build thread.

 

First off, my truck is a 4.0 4x4 5 speed, and an Ohio truck so it's fairly rusty, but I picked it up for a mere $400. It came with 2 complete sets of wheels, zero good tires, and an extra AX15 (internal slave). It did not run. I replaced the starter, a couple injectors with some I had laying around from a few XJs I've had, some spark plugs, and then she fired! Unfortunately, the engine held zero oil pressure (checked with a mechanical gauge, engine was victim to a Fram filter) and had a LOT of blow by and oil burning in the exhaust, along with a seized alternator. With all this in mind, I decided to swap a new(ish) 4.0 into the truck.

[barimpact]

With the engine swap decision in mind, I picked up a 99 XJ for another $400. It was 130k miles, freshly rear ended HARD and totaled. Rust free. in the process of pulling the engine, I parted out some of the other stuff and of course made the money back on it, so free engine. I made sure to hook it up to a fuel pump and start it before I took it, and it ran like new. No CEL or anything. 

 

When pulling the engine, everything came apart fairly easily, even those dreadful E12 bolts on the top of the bell housings. The main things I knew I'd have to look out for in the swap were these:

- Things that were slightly different year to year (intake manifold, alternator, fuel rail, etc)

- Pilot bearing (I'll get into this in more detail later)

 

Otherwise, 4.0 to 4.0, fairly straight forward as far as engine swaps go.

[barimpact]

Fast forward 4 months, I've moved into a small warehouse space and finally have the engine into the truck. Here's some of the important things I found:

 

CPS

For those that don't know, there is a CPS mounted to the top of the bell housing. If you're doing this swap, change out the old nasty sensor! New ones are very cheap and you'll never be able to get to it this easily again.

 

Fuel Rail

Easy, just use the fuel rail from the old engine. Bolts right up, don't have to change the lines, everything's good. If you're worried about the difference in fuel pressure, you can remove the vacuum line from the fuel pressure regulator and bring it up a few pounds.

 

Pilot Bearing

I purchased the pilot bushing from Novak Conversions. It was kind of expensive at $30ish after shipping (depending on what shipping you choose) but it fit PERFECT. I know a lot of people said that it did not fit their application, but it fit mine perfect, no headache. I made sure to grease it up good, but as far as making a 91 AX15 fit into a 99 4.0, it was a dead ringer.

 

Intake Manifold

It is much simpler to use the intake manifold from the old engine, but I wanted to keep the newer high flow manifold on mine, so I made it work. There are a few vacuum lines you have to move around, you have to take the sensors/fittings from the old one and thread them into the new one, and I took the vacuum line that runs from the canister to the manifold (and the newer smaller canister) and it all works out pretty good. I will be making a YouTube video explaining in great detail the things I had to change to make this new manifold work. This will be much easier than trying to explain it here. For now, I've included a simple picture to show how it looks.

 

Cooling System

My Comanche did not come with an electric fan, so I took the one off the Cherokee. I also took the heater control valve out of the truck and just used the coolant lines from the Cherokee to bypass it. Good mod to do to prevent the heater core from clogging when you aren't using it.

 

General Electrical Plugs

All the sensors and things are pretty much the same from the 99 to the 91, but all the plugs are different! I pretty much took every single electrical plug in item and swapped it with the identical item from the old engine. The list includes the intake temp sensor, O2 sensor, injectors, alternator, distributor, ignition coil, EVERYTHING. Don't get rid of the old engine until you fire the new one and make sure everything is running correctly.

[barimpact]

The guy I bought the truck from built his own rear bumper out of 1/4" steel (aka invincible) and I threw on the front stinger winch bumper from one of my old XJ builds. I'd love to restore and make the truck look new, but it's too far gone from the original state to really make this one all original, so it'll have a mild build. On these old style fenders you have to trim straight back directly beneath the headlight to get the bumper to fit correctly, which isn't a big deal to me. The bumper isn't leveled and tightened up yet (much easier to mount a winch with it tilted forward slightly) but you can get the idea of how it sits.

 

I've also started replacing my broken clutch line with stainless steel braided, and I'll be making a video on how to do this as well. There are already a couple very good write ups on how this is done, but I know sometimes it is much easier to see it done than read about it.

[MiNi Beast]

Well organized write up. Pics do help and make up for a lot of words. Good little project you have going and on a decent budget thus far. 

 

What are you doing in regards to the dash wiring, splicing or swapping to 99 dash setup? 

[87Chief]

For the videos, do you have a youtube channel? I'll subscribe.

 

[barimpact]

On 11/20/2019 at 1:00 AM, MiNi Beast1 said:

Well organized write up. Pics do help and make up for a lot of words. Good little project you have going and on a decent budget thus far. 

 

What are you doing in regards to the dash wiring, splicing or swapping to 99 dash setup? 

Thanks! All the wiring in the truck is factory, I'm currently working through some diagnostics to get the truck running like a top. I'm keeping the original interior, the only thing I'm taking from the 99 is the Engine. 

 

On 11/20/2019 at 10:50 AM, 87Chief said:

For the videos, do you have a youtube channel? I'll subscribe.

 

Yes, my YouTube channel is Backyard Builder, the one with 1800ish subs (thanks in advance for +1!). I'll be uploading video of the clutch line in the next day or two, and the info on the 99 engine swap in the next week or so hopefully.

[buxmj]

Just subscribed to your YouTube channel and watched your head light conversion, good stuff! Keep the pics and updates coming here and look forward to more projects from you!  

 

Buck.

[barimpact]

I'm coming close to having the swap to where I would say is a success. The truck starts and runs and moves on its own power, but stumbles and hesitates. First step of course, check for engine codes, even though the engine light was not illuminated. These older systems aren't as quick to turn the light on like the new ones are. After doing this I got 5 codes:

12 - Battery/ECU disconnected in the last 50 cycles 

13 - No change in manifold pressure from start to run 

33 - A/C clutch circuit open/shorted

35 - Cooling fan circuit open/shorted

55 - ECU finished telling you codes

 

Since my truck doesn't have A/C and didn't come with the electric fan when I bought it, 33&35 were no surprise. 12 of course because I have only started it 4 or 5 times since the swap. Here's the website where you can find an easy to read and well organized list of engine codes:

https://www.fixjeeps.com/jeep-check-engine-codes.html

 

For code 13, an easy check is to disconnect the vacuum line going to the sensor and see if there's any change in the way it runs. Mine had no change, so the sensor was definitely bad. 

 

I also checked a few other things. I reset the distributor using the timing mark on the crank pulley, used a multimeter to check the TPS (it was bad, so I have to replace this too). And while I'm at it, went ahead and bought an IAC. They aren't expensive so I'll just start fresh on sensors with the 'new' engine. I've also got to replace a leaky heater core, and some extremely rusty brake lines that don't hold pressure to the rear.

[barimpact]

For those interested, I've got the video uploaded for my stainless clutch line conversion! Here's a quick link to the video:

 

And here's a link to the original thread I used to help get me started on mine:

 

[barimpact]

Today I had the pleasure of replacing the heater core that broke when I was doing the swap. The copper seized to the coolant lines, and when the line came off it ripped part of the fitting with it, which created a leak. Got a new one from Amazon and it seems to work great, blows nice hot air and doesn't leak a drop! Taking the dash all the way apart also gave me the rare opportunity to vacuum out all the bugs, dust, and rodent remains from the years of sitting, and it does smell a lot less musty now.

[Pete M]

great work!  I think that MJ really lucked out when you bought it.  

 

feel free to post your favorite videos in the DIY forum and I'll integrate them into the master DIY list as I get time.   

[barimpact]

Little bit of an update today, the truck is running awesome. I gave it about 1/4 tank of 91 octane and it really seemed to clear up all the hiccups. It's firing right up even after sitting outside all week. In the next week or two I'll really go through the truck and show all the little things I had to do to get the swap completed. Once I get her cleaned up and a matching set of wheels I'll get more pictures!

[barimpact]

Hey everyone, I have recently swapped a 99 XJ 4.0L into my 91 MJ and because of all the confusion I found researching the topic, I decided to create a solid write up on this. My 99 engine still contains the new style intake manifold to maintain the better air flow. This will be mostly text here, but I have created a video for YouTube to show that this DOES in fact work like stock.

 

The first thing I'll say is this: the golden rule to the 4.0 swaps are that newer engines generally work perfect in the old style, but NOT the other way around! And the reason I say generally is because I cannot say every swap will be guaranteed to work. However, for the sake of this write up, I WILL ONLY BE DISCUSSING XJ TO XJ/MJ SWAPS.

 

I recommend you do not throw ANYTHING away until the swap is completed. Having all the parts around may be a little cluttered, but you'll be very happy when you have the old parts to reference.

 

 

DOING THE SWAP

First off, the swap itself. If you are reading this, I assume you have the skills/confidence/knowledge to unbolt an engine, pull it out, and put another nearly identical engine in its place. This is about as bolt in as a swap like this could be.

 

ELECTRONICS

Just about every single plug/sensor there is in the 97-99 engine is DIFFERENT from the pre-97 engines, even though the sensor works almost the exact same. Here's a list of the sensors/electronics you need to KEEP FROM THE OLD STYLE ENGINE:

-Oil pressure sensor

-Coolant temperature sensor

-Coil pack

-Distributor

-Idle air controller

-Throttle position sensor

-Intake temperature sensor

-O2 sensors

-Injectors

-Crank position sensor

-Alternator

-Cruise control actuator

 

There may be some I'm forgetting (as my MJ is a base model), but if it has a plug, keep the old style. Some things you do not need to swap over, like the starter, battery cables, etc. as they are nearly identical. As for the AC system, I do not know for sure, as my MJ came factory with no AC, but I imagine the plugs will be different and you may need an old style AC system.

 

 

NON ELECTRICAL SYSTEMS

There are some things when keeping the new style intake manifold you will need to keep from the old style, but some things it is often better to have the new style. Here are things you should consider with the year model listed beside it:

-99 Power steering pump (the old style bolts on different)

-99 Heater core hoses (I highly recommend a heater control valve delete)

-91 Throttle body (to accommodate the old style sensors mentioned above)

-91 Exhaust (to maintain proper O2 sensor locations)

-99 Intake (of course)

-99 AND 91 Vacuum lines & connectors (See below)

-99 Vacuum canister (the smaller size is just nice to have with aftermarket bumpers, but not necessary)

-99 Fan shroud (not required but nice to have the correct belt diagram)

-91 Fuel system (rail, lines, regulator, etc)

 

Most of the rest of these things are pretty self-explanatory as they are identical year to year, such as the air box and intake elbow and radiator, or because they came with the package, such as valve covers, anything else pulley driven, etc.

 

 

VACUUM LINES

It is important that you take as many vacuum lines as you can, but crucial that you have the vacuum line FROM THE ENGINE ALL THE WAY TO THE CANISTER. This line is easy to remove as it is very flexible. Take all the elbows, connectors, everything. Using the extra vacuum lines, it is possible to connect all the required items to the vacuum system, such as the brake booster, breathers, MAP sensor, intake temp sensor, fuel pressure regulator. Everything that was once connected to the old intake manifold should STILL BE CONNECTED TO THE NEW INTAKE MANIFOLD. Special pieces you may not think to grab are the small canister, as many elbows and plugs as you can carry (since you may come across rotten ones), and the T fitting threaded into the manifold near the power steering pump.

 

 

MISC. ADVICE

Here's what I'd do when doing the swap if I were to do it over again with my current knowledge:

-New CPS while the engine is out (it bolts to the bell housing)

-Replace the alternator while the engine is out

-Do a complete maintenance checklist since you have to replace all the fluids anyways (for example, might as well get a new air filter and spark plugs too)

-Address any known oil leaks (seals are cheap and no better time to do it)

-Flush out the heater core (you may be surprised how dirty it is)

-Clean and coat your floor pans if they haven't started to rust (northern states)

-Check the condition of your brake lines with the engine out of the way

 

 

MANUAL TRANSMISSION SPECIFIC

If you have the AX-15 in your XJ/MJ from before 93, MEASURE YOUR PILOT TIP. if it is NOT a 3/4" tip, you will need a custom pilot bearing. THERE ARE NO AUTO PARTS STORE THAT OFFER THIS ON THE SHELF. I checked AutoZone, O'Reilly, Advanced Auto, Napa, Pep Boys, KOI, and even called around a few small time local stores. I ordered the adapter pilot BUSHING from Novak. This isn't a plug for them, just a product I found that works. Here are the sizes:

 

-Pilot Tip:

--88 to early 92 19/32" Diameter

--Late 92+ 3/4" Diameter

 

-4.0L Crank Bore:

--Pre 92 1-1/16" Crank

--92+ 1" Crank

 

You cannot make the mistake of running without one of these on your manual transmission. It will create a ton of premature wear and ruin the transmission. You must also be careful to notice that if the engine is pulled from an automatic, it will NOT have a pilot bearing, as the torque converter doesn't require one.

 

This is about all the information I can think up right now. If you have any questions or think I made a mistake let me know and I will explain how I came to each conclusion above. PLEASE REMEMBER, THIS IS FOR CHEROKEE AND COMANCHE ENGINES ONLY. I AM NOT DISCUSSING BRINGING IN ENGINES FROM WRANGLERS OR GRAND CHEROKEES. I’m sure that you can but be careful that you ONLY use engines with distributor systems. NOT COIL PACKS.

 

Lastly, I have made a YouTube video pointing out and showing many things I have discussed here, but more importantly, visuals of everything and proof that it works like it would from the factory. Here’s the link: 

 

[barimpact]

Sorry for the blunt and obvious copy paste but it's a good draft and I didn't want to change it up much lol 

[Pete M]

On 12/29/2019 at 11:50 PM, barimpact said:

Sorry for the blunt and obvious copy paste but it's a good draft and I didn't want to change it up much lol 

 

 

you're not the first, you won't be the last.    lots of great info in it.  

[barimpact]

A few projects took priority, and the Comanche sat with a flat tire and a bad starter for a couple months. But today I took some time to get her back on the road. 3rd starter within a year, but I think I figured out the problem and got it sorted out. 

 

Progress towards the end goal though, I got all the lights working on the exterior except for the reverse lights (since they aren't huge priority I didn't look into them yet) and license plate lights (they were deleted with the custom rear bumper). Most of the lights weren't working due to a DIY hack job of the trailer light harness built into the rear bumper. But now I can finally legally drive at night!

[barimpact]

Big news today. This build is about to get real. Picked up some 37s today! Gonna build the truck around these tires to make a sweet little rig. Tires on the truck are 225/75/r15 and the big boys are 37x12.5 r15 Goodyear MT/R

[thecodemonk]

I literally saw this picture on reddit just yesterday haha. I'm excited to see the next step!

Sent from my Pixel 4 using Tapatalk

[barimpact]

With a little cutting and hammering they are able to get me down the road without a lift! Can't turn very tight though  it won't be sitting this tucked for long, but what a cool look!

[CapitalCityPioneer]

On 3/22/2020 at 12:16 AM, barimpact said:

With a little cutting and hammering they are able to get me down the road without a lift! Can't turn very tight though  it won't be sitting this tucked for long, but what a cool look!

I always love the look of the huge tires on very little lift. Too bad when you hit a bump they will rub/destroy the fender!

[barimpact]

Going with the Rusty's 3 inch for the time being. I wanted to go as low as I could with the option of adding long arms in the future.

 

Once the lift is on I'm gonna need ujoints basically immediately, as well as brakes. Gonna do the 96 brake booster upgrade that I've read about to see how much of a difference the dual diaphragm setup helps with these big tires. The hubs are in surprisingly good shape, they're definitely not original

[macbon]

Looks great. Those massive tires make your rig really aggressive! How's their performance in the mud and dirt? I'm planning to get bigger tires after I'm done adding a lift. The bfg tire and goodyear are my options.

[Pete M]

bumpstops are your friend   uptravel is overrated! 

[barimpact]

On 4/2/2020 at 10:45 PM, macbon said:

Looks great. Those massive tires make your rig really aggressive! How's their performance in the mud and dirt? I'm planning to get bigger tires after I'm done adding a lift. The bfg tire and goodyear are my options.

 

I haven't gotten to take it out yet due to the COVID-19 pandemic, all the parks are being forced to close due to MASSIVE amounts of people trying to spend their outdoor time wheeling. Plus my gas tank is more rust holes than fuel storage so that's my current project!