Hey all. Just did some trading and picked up this 92 5.8/5spd 4x4 with 4:10s and a wrecked 96 PSD parts truck.

The 92 has 268k miles. It's in overall very good condition considering it's spent most its life on a farm. It's running pig rich and getting about 4mpg. Clutch is slipping occasionally. I'm most concerned with the way it's running as I can baby the clutch but 4mpg is gonna kill me quick. Here are the codes it's throwing:

051 ECT Sensor
126 MAP Sensor
122 TPS
112 Intake Temp Sensor
513 PCM Internal Voltage Failure
327 EGR Valve Position Circuit
550 Air Management Sensor
565 Canister Purge Valve Solenoid
556 Fuel Pump Relay
558 EGR Valve Solenoid
117 Coolant Temp Sensor

Among a few others.

I started with the MAP, as it seems most of those codes could be attributed to it if it were bad. I unplugged it to see if there was a change in the low, irratic idle, or the rich condition. No change, therefore, there must have been a problem with it. I replaced it with a new one but no beans. Still running the same. Wondering if anyone's got some pointers.

The plan for the rig is to get it running right, do a clutch, maybe a D60 swap, more fuel efficient gearing, and fix the rust. Hopefully, it'll then be ready for another quarter million miles.

Here are some pics:

 

Your truck will display two or three digit codes, not both. How did you check for codes and when were they displayed? i.e. during the Key On Engine Off (KOEO) tests, Continuous Memory (CM) display or from the Key On Engine Running (KOER) tests. Your truck could display either series. Ford started to transition from two to three digit codes in 1991.

It is highly suggested you run the KOEO/CM tests first. Once any issues there are resolved then move onto the KOER tests.

 

From that set of codes you're most likely going to need an engine computer. I would suggest pulling it out and opening it up to look at the board inside. If you find any kid of black or blue build up or any burns anywhere specifically near the 3 blue capacitors you've found your issue. If you'd like I can post pics of my bad one I just had to replace for reference.

I had all those same code fyi

 

I'd be much obliged if you could post the picture. Thanks!

 

Before anyone starts condemning a computer let's figure out if the codes are valid. Let me point out a VERY important fact......you will not get a mixture of two and three digit codes. It's one OR the other.

 

I'll run the codes again.

 

I wasn't condemning the computer, I told him to take it out and check for obvious signs of damage. Also the code 513 he listed is almost the computer condemning itself. The easiest check you can do is pull the plugs off your sensors it listed and see if you have a 5v vref to any of them. If not, the pcm either isn't receiving any power, or is bad.
But since you could pull codes, that 99% says it has all the power it needs.

Here's what mine looked like, notice how all the blue can capacitors have burns and corrosion below them:

 

If you aren't getting a 5 volt reference TO your MAP sensor, you either have a wiring or a computer problem. I just had these same issues you have but with my 460 truck. Except I couldn't get any codes at all because I couldn't do the KOEO tests due to the computer keeping the fuel pump running constantly (the test turns on the fuel pump and turns it off) so long story short an $85 junk yard computer fixed my problem.

 

Check the TPS and MAF wires, one wire should have about 5 volts compared to battery ground. If you don't have that, the computer is more than likely damaged.

 

So for kicks and giggles, I pulled the ecu. Bam. Had the same burnt out capacitors. Not as bad as those above, but definitely fried.

Can't find a replacement ecu for the life of me.

 

your local part store should be able to order a remanufactured one for you.

 

Let me clarify my previous statement. I can't find one for less than $100 for the life of me. LOL. Can I run an automatic computer on my manual? I've done it on other Fords with EEC IV. I assume I can on this?

 

Yes you can run an automatic based PCM but you will have a constant Check Engine Light and you may suffer other drivability issues unless you hook up a MLPS and lock it to Neutral or Park even then it is a band-aid solution with mixed results.

 

So, after an hour or so rummaging in the j/y, I scored a 5.8/5spd ecu from a 1990 250. Popped it in, and baddaboom. Perfect running and driving truck. Score.