Ok if you are putting a '93 4.0 engine into an '86 you are doing
more or less the swap I completed last month.
I put a 1993 Explorer engine into my 1987 Ranger supercab.
the 1993 is an "orphan year" as the 1993 engines were different from
the engines made before and after.
The other "complication" is that the 1993-94 Ranger engine bay is layed out
differently, the computer is mounted in the drivers side firewall (like an F-150)
and the battery and Electrical distribution are all moved to the drivers side
inner fender. So using a 93-94 wiring harness takes a big job and makes it
into a monumental one (not quite on par with trying to put a Merlin engine
into a '57 chevy, but...)
The Explorer's retained the same basic engine bay layout until 1994,
but a 1994 Explorer harness is useless to you, 1994 4.0's are SEFI
and have EGR, trust me the extra coimplication of a failure prone
synchronizer isn't something you want, then there is the additional
annoyance of the EGR system that while the system itself is reliable
enough that it would be un-noticeable, the sensor that monitors the
EGR system is one of the most failure prone parts I can think of on
short notice.
The ONLY harness that will work and not be a complete nightmare
to fit in is a 1993 explorer harness
But in using a 1993 harness there are "choices".
the 1993 is two generations removed, not in the engine
management but in the power distribution.
The 1993 eliminates all but three of the Fuseable links
(fuse wires) and two of those are parallel in the battery
cable between the starter solenoid and the alternator.
(the last one feeds power to the DUAL Oxygen sensors)
All of the others are replaced with Maxi fuses.
The Relays are ALL relocated to plug-in sockets in the power distribution box
There are a BUNCH of wires related to the ABS system that you'll
get to eliminate (in my truck I used those two relay sockets for my
Fog and Driving lights)
I CANNOT talk you through the job wire-by-wire
so you WILL need to get the EVTM manual for both your vehicle
AND for a 1993 Explorer (Search ebay for them Expect to pay less than $20 each)
One "twitchy" thing you'll have to deal with is the differences in control
for the AC and heater blower.
The switch for the blower doesn't control the blower directly but instead
does it through another relay in the power distribution box
I had only one problem on my job (a ground wire I forgot to connect)
but then again, I learned to do my wiring building various "black boxes"
for military aircraft...
The wiring alone took me a SOLID two weeks (12-ish 12hour days)
but I am very precise and wanted to do things a certain way.
I did not allow myself to make ANY modification whatsoever
to the harness from the computer to the power distribution box to the engine.
I did not allow myself to modify (even slightly) the factory Dash harness
or the bundle of connectors against the firewall.
what I did was to take two SPARE harnesses (one for the '93 and one for the '87)
and made an "adapter" bundle to connect the two.
But I hacked the everloving crap out of BOTH harnesses that crossed
the front of the truck on the radiator support.
I kept power wires moving from the passenger side to the drivers side
and I kept the lighting and control wires heading in the other direction.
what this accomplished is that ALL of my splices were done in the
left front corner of the engine bay, basically in the area immediatly
behind the windshield-washer/coolant reservoir.
BTW, while the 2.9 Y-pipe will "bolt up" to the 4.0 manifolds you
will have one problem, the '93-94 4.0 engines use seperate HEGO
sensors for each cylinder bank, so this REQUIRES a different Y-pipe
which sadly also requires you to use a later catylitic converter with it...
You can greatly simplify your wiring and conversion issues
in several important ways if you use a 1991-92 Explorer or 1990-1992Ranger
wiring harness.
The earlier 4.0's use a single HEGO which would allow you to use your
current Y-pipe and Cat, though I'll point out that the '86-87 Cat and Y-pipe
are problematic, the flange WILL rot and WILL create a leak.
The Earlier 4.0's wiring and power distribution is far less complicated, though there will be one thing you'd need to change on your engine.
The 1990-92 Computers are not compatible with the '93-94 Injectors.
I must stress that the later injectors are not "Better", nor are the
earlier ones "inferior" they are DIFFERENT.
but you MUST use the injectors with the proper computer, so if you elect to simplify your wiring job it'll cost you a trip to the junkyard for a set of earlier injectors.
AllanD
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