Bunch of codes after swapping 1988 Ranger ECU into 1986 Ranger

[kxri318]

1986 Ranger 2.9 auto, ECU from 1988 Ranger 2.9 auto. The truck has been randomly missing for the last 2 years, replaced or checked literally everything except fuel pump, filters, and most of the wiring harness. Kept getting EGR codes even when all EGR related components were tested/replaced. I decided to just swap in a 88 Ranger ECU, temporarily remove EGR related components and vacuum lines, and make a block off plate for the egr and see what happens. Still seems to run nearly the same with the exception of it idling pretty low now (550 rpm), but that wasn't a big concern right now. It runs stupid rich, like 11 MPG, reeks of raw gas, and smokes everywhere kind of rich. Ran that rich before ECU swap too. Fuel pressure and regulator are both in spec and good. IAC valve doesn't seem to bring idle back up when the alternator is loaded up, also idle doesn't change when unplugged at warm idle. Unplugging the IAC does change the idle when its a high idle at cold start. Just weird behavior

I scanned it after taking it out for a 20ish min drive and got some KOEO codes and KOER codes, but not 100% sure what they mean in my current case. I didn't try driving it on the highway so overdrive was never used during the test drive.

KOEO
_______
86 - Adaptive fuel limit reached or 3-4 shift solenoid circuit failure.
95 - fuel pump secondary circuit fault
29 - insufficient input from the Vehicle Speed Sensor or programmable speedometer/odometer module

KOER
_______
18 - Spout circuit open or spark angle word circuit failure
74 - Brake on/off switch fault; not actuated

 

[Shran]

Well that first code (86) is probably because your '86 transmission is lacking the 3-4 shift solenoid that is present on 1988 transmissions. Probably nothing you can do to fix that one easily.

The rest seem like faults caused by wiring - have you gone through and cleaned up all the grounds under the hood and in the cab? Melted/broken wires anywhere?

Running rich, do you have a catalytic converter on it? If not it'll smell terrible no matter what. But 11mpg is not good. Have you left a fuel pressure gauge on it overnight to see if it drops, indicating a leak?

 

[kxri318]

Well that first code (86) is probably because your '86 transmission is lacking the 3-4 shift solenoid that is present on 1988 transmissions. Probably nothing you can do to fix that one easily.

The rest seem like faults caused by wiring - have you gone through and cleaned up all the grounds under the hood and in the cab? Melted/broken wires anywhere?

Running rich, do you have a catalytic converter on it? If not it'll smell terrible no matter what. But 11mpg is not good. Have you left a fuel pressure gauge on it overnight to see if it drops, indicating a leak?

I cleaned up every ground I could see inside the engine bay. Any others outside of the engine bay I haven't looked at. No melted or broken wires, but some have frayed shielding and some wires near a few connectors have the casing slightly stripped back. The catalytic converter blew itself out before I got it lol. I don't care about the smell, it was just something that allowed me to tell there's a lot of unburnt gas. I didn't leave a fuel pressure gauge on overnight but I did leave it about 20 minutes with no significant drop. When googling, some people said that code 18 could indicate an issue with the ignition control module wires and I extended mine to the inner fender. I'm assuming I didn't shield it enough, but I made it easily reversible so I could try putting the module back in the stock location in the next few days and see if that clears up that code. I do wanna mention it seemed to misfire like this even before I relocated the module, so I'll probably try to replace the frayed shielding of any wires I can find first then undo the relocation if the code persists.

 

[RonD]

Yes, code 86 is because older A4LD trans doesn't have 3/4 shift solenoid, won't hurt anything, but will never go away

Code 29 as well, 1986 harness may not have wiring for speed sensor to ECU since it wasn't needed unless there was a 3/4 shift solenoid

Code 95 means ECU didn't detect 12volts at the inertia switch with key on
Just clear it and see if it comes back, engine wouldn't run at all if this code was correct

74 is a test code, ignore it

18 is interesting if it re-occurs
When was the last time you set the base spark timing?

What were the compression test results?
First test when there is rough running or misfires is a compression test
You can chase your tail with spark and fuel if you don't do compression test first

 

[kxri318]

Yes, code 86 is because older A4LD trans doesn't have 3/4 shift solenoid, won't hurt anything, but will never go away

Code 29 as well, 1986 harness may not have wiring for speed sensor to ECU since it wasn't needed unless there was a 3/4 shift solenoid

Code 95 means ECU didn't detect 12volts at the inertia switch with key on
Just clear it and see if it comes back, engine wouldn't run at all if this code was correct

74 is a test code, ignore it

18 is interesting if it re-occurs
When was the last time you set the base spark timing?

What were the compression test results?
First test when there is rough running or misfires is a compression test
You can chase your tail with spark and fuel if you don't do compression test first

Last time I set the base timing was a few months ago at 11 degrees BTDC. Don't remember the per-cylinder results but it was all within 7% of each other from 137.5 to 147.5 psi with no outliers being way lower than the rest or anything. I ran the compression test a few months back near when I set the base timing. Later today I'll try to find time to fix the frayed shielding on the stock wiring harness then try to do a cylinder balance test because I found out my scanner can do that.

 

[kxri318]

Last time I set the base timing was a few months ago at 11 degrees BTDC. Don't remember the per-cylinder results but it was all within 7% of each other from 137.5 to 147.5 psi with no outliers being way lower than the rest or anything. I ran the compression test a few months back near when I set the base timing. Later today I'll try to find time to fix the frayed shielding on the stock wiring harness then try to do a cylinder balance test because I found out my scanner can do that.

Fixed the frayed shielding, no change, still runs the same and get the same code. Tried to do the cylinder balance test, but it didn't work. Its supposed to rev the engine up a little and start cutting fuel to each cylinder to test which one isn't contributing the same. It revved the engine up once, then it idled back down and didn't do anything for several minutes of having it idle after that. I'm leaning towards the misfiring being a wiring problem because my dash light fuse blew out for like the 5th or 6th time for no apparent reason, finding a melted connector for the ignition switch once, the weird issues with the IAC valve, and biggest of all I'm quite literally out of things to test/replace besides trying to put the ICM back in the original spot. I'll try that tomorrow and update if it clears any codes/makes a difference but I doubt it considering it ran like this before I extended the module. I really appreciate all you guys always helping out though