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Unread 06-07-2011, 11:14 AM   #1
brobich
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1987 YJ Wrangler 
 
Join Date: Jun 2011
Location: southeast, texas
Posts: 23
4.0 obd2 conversion on a yj

hello all jeepers, i need some help. i just bought my first jeep, its a 1987 wrangler. needs a motor, i got a 1996 grand cherokee limited donor. i have started pulling the motor and te huge wiring harness. i have pulled the harness from the passenger side fuse panel all the way around to under the stearing coloum, not cutting wires. i am wanting to install this motor and harness in my yj. what wires can i cut out, and what wires do i need for the comp to run the engine. would it be easier for me to go to the obd1 or can i modify the obd2. i've read its easy to do the obd1 haven't read much on the obd2. any help would be thankful.

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Unread 06-07-2011, 02:35 PM   #2
ihategp
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1990 YJ Wrangler 
 
Join Date: Nov 2008
Location: grants pass OR
Posts: 58
just did this on my 90 used a 96 motor also. it was real easy to wire took just 4 splices if i recall. biggest problem was the fuel. the 96 is regulated at the pump not on the fuel rail. but you can use a external fuel pump and regulator to get by that. dont forget you will need to run both o2 sensors. you can pm me if you have questions on the wires or any of the other parts needed.
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Unread 06-08-2011, 06:17 AM   #3
brobich
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1987 YJ Wrangler 
 
Join Date: Jun 2011
Location: southeast, texas
Posts: 23
4.0 wiring

thank you for the info you pm me that eases my mind a lot. just curious the wiring harness that comes off the engine, is the one that i need to be concerned about, i can trace out the wires for that system back to the fuse box and computer , do away with all wires that do not tie into that system. and still leave the three connectors plugged into the comp just cut and heat shink the ends. to the wires that i dont need. also can i hook up my data link by splicing into the comp with the wires that i need to pull codes?
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Unread 06-08-2011, 08:12 AM   #4
brobich
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1987 YJ Wrangler 
 
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Location: southeast, texas
Posts: 23
also can i use the flywheel for a 91-95 with the obd2 or do i need one for a 96 4.0?
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Unread 06-08-2011, 12:11 PM   #5
ihategp
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1990 YJ Wrangler 
 
Join Date: Nov 2008
Location: grants pass OR
Posts: 58
i removed all the wires out of the harness that went through the firewall only left what was needed for the sensors and such. any flywheel for a 4.0 should work. looking on napa's site the part numbers are the same from 91 to 99. as far as the data link i have yet to wire mine in. but from the grey connector on the ecu it should look like this

data link- ecu
7 pink -c27
11 wht/blk- c28
6 lt grn -c29
3 vio/brw -c30
4 blk just ground anywhere
5 blk/lt blue also gorund
16 tan/blk fused power

like i said i have not wired mine in just going off the diagrahm i have.
if you are going to use the hesco cps kit then you should not need to change the flywheel just use the one from you 258. i over thought the whole wiring and really didnt need to was much easier then what i thought it would be. doing this swap made it seem like a whole new jeep went from 10mpg on freeway to getting 18mpg
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Unread 06-08-2011, 12:34 PM   #6
brobich
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1987 YJ Wrangler 
 
Join Date: Jun 2011
Location: southeast, texas
Posts: 23
4.0 wiring

cool deal, thank you for the info. i have the ax-15 withe the cps hole ill just use that like it came. (flywheel is cheaper than the conversion lol) ill let you know how things come out, going to work on it this weekend.
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Unread 09-03-2013, 04:19 AM   #7
lbsickboy
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1986 YJ Wrangler 
 
Join Date: Aug 2011
Location: Den Haag, zuid holland
Posts: 190
Quote:
Originally Posted by ihategp View Post
i removed all the wires out of the harness that went through the firewall only left what was needed for the sensors and such. any flywheel for a 4.0 should work. looking on napa's site the part numbers are the same from 91 to 99. as far as the data link i have yet to wire mine in. but from the grey connector on the ecu it should look like this

data link- ecu
7 pink -c27
11 wht/blk- c28
6 lt grn -c29
3 vio/brw -c30
4 blk just ground anywhere
5 blk/lt blue also gorund
16 tan/blk fused power

like i said i have not wired mine in just going off the diagrahm i have.
if you are going to use the hesco cps kit then you should not need to change the flywheel just use the one from you 258. i over thought the whole wiring and really didnt need to was much easier then what i thought it would be. doing this swap made it seem like a whole new jeep went from 10mpg on freeway to getting 18mpg
Hi

Im have the OBD2 set up to , it came of my xj 97 i have every thing i need but i just not to sure which way and what to connect,
here is a link on how far i am, check my signature links.
im in desprate state cant get the jeep to turn over
all my wiring is ready and labeled both xj and yj.
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http://www.jeepforum.com/forum/f12/4-0l-xj-97-motor-into-yj-87-a-1567705/
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Unread 09-16-2013, 06:13 PM   #8
wrangler1990yj
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1990 YJ Wrangler 
 
Join Date: Sep 2013
Posts: 5
I just wanted to verify what I read above b/c I'm also swapping in a 98 xj 4.0 into my 1990 4.2 yj ax-15...So, I can retain my stock flywheel when swaping this engine in ?

Thanks a million!
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Unread 09-17-2013, 03:40 AM   #9
Que89YJ
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1989 YJ Wrangler 
 
Join Date: Apr 2008
Location: Detroit, Michigan
Posts: 14,545
no you need the 98 flywheel if you are using the stock crank position sensor or the hesco? Hesco yes the stock cps then you need to change the flywheel.
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