NEED HELP! Truck idles low and won't restart after warm.

[Rjack90]

89 Ford RaNGER 2.9 Manual trans swapped in a reman 4.0 and used 91 ford ranger auto wire harness
Made this swap a few weeks ago. The biggest difference on electrical was the C105F (FireWall Big white connector Plug) Repinned and got everything working for the most part. Guages lights etc. Truck ran good for a week put about 200 miles on in it. Went back into plug and swapped two pins thinking I was fixing the radio memory issue. It was a black/white (12 volts) not being used from 91 harness into a slot 14 which in the 89 was a black white that I now know an to Clutch PS, ABS and Manual trans. Cranked motor over and got no start. Switched wires back. Truck fired up but all the sudden had low idle and now a check engine light on of the first time. I drove the truck around 10 minutes ran good still low idle (500rpm) but wouldn't die all gauges read good but CEL stayed on. Turned it off and went to restart, it just cranks.
I have spark, fuel, fuel, pressure, injector pulse. But truck will not restart if warm. If it sits for 15 20 minutes it will fire right up, CEL pops on in 5-10 sec and idle goes low within a minute. Truck will run until you shut it off. Once off and go for restart it will not fire just crank.
I replaced TPS, Coil pack, Swapped 3 EDIS6, New MAF, New IAC, New temp sensor, HEGO sensor. Checked all fuses and relays (Initially had HEGO fuse blown, replaced and now good)
No more fuses blowing and still same issue.
I started checking grounds to EDIS 6 plug. Black and White ground is good to power ground but the Ignition ground Orange and Red coming from computer is reading 5ish volts? Why would this be? I have read a poor or bad ground to the ECU but I am not finding anything burned.
I believe this is the problem any help on next move would be greatly appreciated.

I also checked continuity on blue wire and grey wires going from EDIS to CPS they tested good. All yellow ignition wires should be good because its firing.

 

[SenorNoob]

Since you say you a black/white with power, I wonder if the ground to ECU (black/white) ended up positive at some point and burned a circuit in the ECU.

If so you should be able to see it by opening the ECU up and looking for charred spots. If you haven't already.

When you get a check engine light, can you pull codes?

Best I can tell, the ECU should ground the Orange/Red to power the EDIS. I wonder if you could ground it directly to get spark back?

 

[Rjack90]

Yeah that’s what I thought. I opened the echo and all looks good. Even swapped with two others from 94 explorer AT they run even a little lower in idle.
I tried to OBD1 test but will not read any codes. Either light just stays lit or sometimes it will go out when I put the jumper wire in but no flash.
i will see if i can just ground the ECU ground direct or test it to see it it’s open.
Thanks

 

[Rjack90]

ECU not echo

 

[Rjack90]

Still no luck. I tried cutting the orange red ignition ground wire. left it open coming from ecu and ran it straight to negative on batt from edis. It cranked no fire. I hooked it back up.
I tried taking the three grounds that run to ecu, two power grounds and one case ground. I ran a lead connecting all three and ran straight to negative on battery. Truck fired right up and I thought I found it. Turned it off and went to restart and just cranked.

Had another strange electrical situation. The fuse for the courtesy dome light kept blowing. I pulled it out. Drove the truck into a mechanic to look at it, open the door and the dome light comes on with no fuse in the slot?
(mechanic was not much help he plugged in a obd1 reader and it would not give any codes) he recommended swapping the harness

Im thinking a main ground burned to a positive hot wire and now it’s sending voltage through the ground. Hopefully it is in the engine bay wiring harness because I am to the point where I am just going to pull it and swap itvwith another from the junkyard.
Any thoughts or other ideas would be greatly appreciated!

 

[SenorNoob]

If there is a power to ground somewhere, shouldn't it be getting hot, blowing fuses, or draining the battery at least?

 

[Rjack90]

Yeah you would think. I’ve blown a few fuses inside cab fuse panel like the courtesy dome light and HEGO. They are no longer blowing and no blown fuses in PCM.
Im having a hard time nailing it down. I was going to start removing the hot wires feeding the firewall plug 1 at a time to see what is needed. Currently there are 5 12 volt leads going in.
I will also test the grounds going to ECU and see if there is voltage coming out of them, hopefully there is so I can pin point it.