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Jboys 86 MJ build


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hey guys. not new to jeeps but new to comanche's.

 

I never thought i would own 2 jeeps but here we are.

 

So this is not so much a build as it is a make this a work truck!

 

So it started with an 1986 MJ with 2.5 TBI 5 speed? and np207 and 160xxxkms. The 5 speed was not in great shape so i had to tow it home (about 300kms).

 

 

So went to uhaul and got a car hauler. it was an interesting trip to say the least.

 

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It was a lil dark out but here are some pics in the light

 

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original buckets have been swapped for a bench but the owner still had the original buckets and center concole.

 

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some $#!&ty 31's

 

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now the engine only has 160,xxxkms but has a good oil leak and a fubar'd trans

 

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So i was looking for a new trans when i heard "johno" from a local board here "www.bcjeepclub.ca" was selling the complete drivetrain from his TJ as he is doing a 4.0L swap. so i spent all day yesturday pulling his drivetrain.

 

98 TJ 2.5L MPI ax5 and np231 has about 200,xxxkms

 

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Now I was originally gonna just pull the trans and swap it with mine. but the more and more i inspect the mj the more and more and more oil i find.

 

so i think i will just swap the entire drivetrain as i have the complete wireing harnes and everything. the engine has a slight knock and more kms but is 12 years newer. is MPI vs TBI and has little to no leaks.

 

Anyone with info on this swap or tips or whatever please speak up.

 

While this is a "work" truck i really can't help myself...

 

so i can see an 8.8 swap in the near future. lift? ect ect. and maybe some new seats.

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So here are my issuses. i have searched this quite a bit but have come up somewhat empty handed. i know this has been done before but i can't seem to find all the answers.

 

the comanche is a 86 and has the 2.5L TBI 5 speed manual(ax5-Ba-10?) and the np207?

the enhine has 160km and a large oil leak from somewhere. the oil is everywhere.

 

i have a comple 98 tj drivetrain

 

2.5MPI ax-5 and np231. no oil leaks and the entire unmolested wireing harness.

 

can anyone tell me of any issues i am gonna run into? i also have access to all the gauges and dash clusters if need be. pretty much the entire tj.

 

so any pointers would be GREATLY appreciated!

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no i am with ya man. thats why i am here. i appreciate everything.

 

any chance you happen to know if the wireing harness from a 2.5 mpi is plug n' play with inner harness of the 2.5 tbi. i am assuming i am gonna have to splice either the cherokee mpi harness to get the guages to work anyways unless i get an updated dash?

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  • 1 year later...

Well...i havent posted much on this but there is lots to post.

 

Now before you read on I'm just gonna go ahead and say it now. don't do this swap. don't attempt this swap. don't dream of this swap. It's not worth the money or time.

 

Ok with that out of the way....

 

We have a 1986 MJ chassis and a Engine, Trans and TC from a 1997 TJ.

 

The goal was to replace the 1986 2.5L TBI to a 1997 2.5L MPI. The TBI engine had a massive oil leak. Pulling the engine was the easy part. The nice thing about this swap is its mostly a direct fit. Because we were doing this on the cheap (at first) we cut a few corners if you will. Upon inspection the trans had serious issues. 1st gear stripped and the clutch master wasnt plunging. The return spring had rusted and busted. So it had to go

 

The 2.5L MPI was put in place. To save money and not have to buy a new eternal slave we reused the older Bell housing. (internal slave) Mistake #1 as in its a b*@$£ to service and bleed. Well not so much a mistake but just a real pain in the @$$. Then the newer AX-5 was put in place to replace the shot BA-10. We kept the NP-207? instead of putting in the NP 231 becasue the speedo is mechanical and to work with the current speedo it had to be retained. also the CAD axle needs a vacum sorce from the TC to activate. And this way a new drive shaft would not have to be made as the outputs are different. The 231 TC does have a mechanical speedo however the signal is sent to the ECU and a signal is sent to the gauges in a TJ. The 207 has a small wire that spins inside a tube right to the speedo. The best solution to using the 231 i think would be to find a dash cluster from a newer XJ that already has a 231. In fact a whole dash asembly and harness may have made a bunch easier. however we didnt have it, so on we go. That could be counted as mistake #2.

 

The exhaust on a TJ comes off the header and wraps infront of the oil pan and down the passenger side of the vehicle. The MJ exhaust goes under the oil pan (the oil pan is scalloped) and then down the passenger side of the vehicle. so the TBI oil pan was pulled off as well as the oil pick-up and swapped onto the MPI engine and that way the exhaust could be hooked back up without modification.

 

I believe that was pretty much if for the mechanicals. Next was the electronics. I did none of this. My dad took this part on and I think it aged him a good 10 years.

 

So if i say something that makes no sense it cause I'm taking out my @$$. First issue is the fuel. TJ's have no return fuel line back to the tank. MJ's do. Also the fuel pressures are different. A summit racing regulator was put in place. it has a has a return line back to the stock tank and a constant to the engine. So problem solved. Next was with the iginition. The TJ's have an anti theft key that had to be bypassed. Also the ignition has an Accesory position, on poisition and start position. The MJ colum had an on position and start position. (may have been solved with a new colum Mistake 3?) The lack ok this position caused havok withe the ingition and anti theft in the ECU.

 

Timing is internally regulated in the ECU and we never could get it just right. So he pretty much stripped the TJ harness to its bare bones to make the truck run. Good thing there is no check engine light on the MJ dash casue it would always be on. There were chassis ground issues. Engine ground issues. and many more i can't even remember. Basically he was rewiring this thing for a good 4 months. I can't even begin to explan all the issues as most of it is over my head.

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The truck ran for me for about 10 months before it just shut down. It failed around november 2011. Apparently the first TJ's were plagued with wiring issies. But it was hit and miss. Either you got $#!& wiring or you were fine. Guess which set i had... :'(

 

Yup it was starting to fail. there was a short somewhere and it was blowing the run/start relay and shutting the truck down randomly. My brother had bought an older ski boat and him and my dad were putting in a 302 small block and swapping in an EFI system. so he had been researching this company.

 

http://www.diyautotune.com/

 

So we completely scraped the stock ECU and wiring harness and made our own.

 

He selected the kit for our application and literally built a new ECU. Soldered in new resisters and transisters and doo-dads and entered the matrix. Then did a full rewire. No $#!& wiring. No $#!& stock ECU.

 

We were able to set our own parameters. our own timing. Basically we got the parameters as close as we could. set our cold start. and our air fuel mixture. You get it close and then the ECU self learns (to a point). The company says get the parameters close then take it to a dyno and get it tuned. They said you can mess around for months or spend an hour on the dyno and be done with it. So today thats what we did. Not gonna lie. seeing a 2.5L 4 cly MJ at the dyno was pretty funny. We went to 5252 motorsports and i must say they were really great. the owner did our dyno tune.

 

http://www.5252motorsports.com/

 

 

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Notice the bottem end knock! Oh $#!&ty 4cyl.

 

He started off just tuning. changing loads. (boring vid)

 

Here are the stock specs for a 97 TJ 2.5L MPI (copy&paste from jeepforum.com)

 

2.5L I-4 151 cu in - 1997-2002

* 120 hp @ 5,400 RPM

* 140 ft/lbs @ 3,500 RPM

* OHV

* Sequential port fuel injection

* 2 valves per cylinder

* Compression ratio = 9.20:1 (97-00) / 9.10:1 (01-02)

 

Here is the power pull...

 

 

The results.

 

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89.1 HP and 145 ft/lbs of torque at the wheels

 

That aint bad for an engine that has 250,xxx km on it.

 

The engine has a cold air intake and was tuned but still. better than i thought. concidering 20-25% loss for a 4wd drivetrain. puts me right back up with power levels from the factory.

 

I was expecting worse.

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