I'm trying to complete the engine swap but I've run into a dead end. I bought a donor vehicle, a 97 F250 HD (OBS). After building the engine, and physically doing the swap, I tried the harness from the 97 (had to move a couple of pins), and got the engine running, but I'm missing the Tach, possibly speedo, and I don't know what else using the 97 computer. The 97 harness has 4 fewer pins than the 94 at the junction block where they come apart. I've looked all over and I can't find a 94 V8 engine wire harness. I have a computer inbound for 94 5.8L with manual Trans, but Im stuck on the wire harness. When it gets here I'll try it with the 97 harness as I have nothing to lose.

How close is the harness from a 95 V8? I've found multiple 95 harnesses and am tempted to try, but don't know what I'm up against. At least the 95 seems to have all the pins the 94 has. Any suggestions??

 

Were either of your trucks mass air?

 

No, both were SD trucks. Apparently the HD 250's were SD's until they quit making the engine at the end of 97. Most of the 95's (5.0 and 5.8) I'm seeing are also SD trucks.

 

There were mass air HD trucks in California and maybe also in California required emissions states? From what I understand manual transmission trucks were speed density but automatic trans truck could be either. It depends on model year.

 

You say you got the 5.8 running, was that with the 4.9 computer or the one from the donor truck? Have you tried pulling codes?

 

Conanski:
I have not tried to pull codes. Thus far the CEL has not come on. I used the donor truck computer, which was for the 5.8 with a E4OD 2WD trans. I'm using a manual trans (NP-435) and an old school transfer case 4WD, and would imagine there are codes related to trans (or lack of trans feedback). I had some issues with the IAC when I got it started, in that it energized as soon as the key was turned on, and made the truck "idle" at about 2500 rpm! I kinda think it may be the TPS shooting bad info, but the engine idles pretty well without the IAC connected. I need to test the TPS, but have not yet done so. I'm thinking it may be sending voltage at rest indicating an open throttle condition which causes the IAC to energize. I intended to put a 94 engine harness in, test the TPS while I have the upper intake off again. On the 95 harness I pulled, the female side of the connector looks just like the 94 6 cylinder female connector. My plan is to ensure base timing is accurate, check the TPS and try the 94 computer to see what happens. My last step is to try the 95 harness with the 94 computer. I'm running out of ideas since I can't find a 94 harness...

 

The problem you're suffering with is because Ford changed the wiring frequently. What you should do is buzz out all the wires on the I6 engine harness and make a table of where they go at the bulkhead connector, and compare that to the V8 version that you have. The two motors use all the same EFI components they are just in different locations, and both use 2 injector batches, the V8s just have 2 more connectors on each string. Any extra wires in your '97 harness you can ignore, any you need that go to the wrong connector pin you move. You should be able to make that harness work.

 

Conanski:
Many thanks, sir. The 97 was missing several circuits, so I procured a 95 wire harness that had the right number of circuits. Did the pin out table as you suggested, and like magic, once everything agreed, she fired up and everything works. Still fighting with TPS/IAC high idle issues, but I'm sure I'll work that out. May be a computer "learning" issue. Time for some mufflers and driving! Thanks for the advice!
Tracker 401

 

IAC-How to Clean and Test your IAC - Ford Bronco Forum
TPS-Throttle Position Sensor Testing, Replacement and Adjustment - Ford Bronco Forum

 

The PCM take a snap shot of the TPS voltage at every start and uses that as the reference, but the closed throttle voltage still has to within an acceptable range.. close to but not over 1v, and there cannot be any dead spots in the TPS voltage as it sweeps to WOT. Glitchy tps sensors are not unusual but so are gummy IAC valves or dead control solenoids so there are lots of ways these parts can lead to idle problems.
Of course if there is an unmetered air leak into the intake that would cause a high idle too, a missing or broken EGR valve, a leak at the brake booster or a gasket leak are possibilities too.

 

When I did the engine swap, the first time I fired the new engine up, the IAC had the truck running at about 2500-3000 rpm'S. To correct that a buddy tried to lower the rpm's by backing out the TB stop screw, to no effect (What can I say, he's a Chevy guy). I then unplugged the IAC and things settled down...a lot! After I changed to a 95 wiring harness, things went much better, with rpm's going only to about 2K. Based on links provided and a bunch of reading I was able to reset the stop screw to the TPS voltage was at .93-.94VDC with the key on, engine off. When fired up, it initially jumps up to 1500, and in about 30-45 sec, will settle down to about 1,000 - 1,100 rpm. I'm hoping adding a little back pressure (mufflers) and some local driving will cause things to settle down a bit more. It's a reman computer for a 94 5.8 with MT. All in all I'm pretty pleased with the engine swap and the way it seems to run. Been out of town, so mufflers are a 1st of next week issue. My truck is now officially a Frankenstein truck...77 4wd running gear, NP435 trans and NP205 TC, with a 94 frame, body and computer, with a rebuilt 97 5.8L SD engine (from an F250HD). Using a VIN for anything is a waste of time and effort!