I have a rough running 91 F140 5.8l fuel injected. I am trying to figure this beast out. I pulled the key on engine off codes, but do not know which code to start with or where to start. Here are the codes in the sequence they arrived.
61, 66, 22, 63, 64, 31, 67, 19, 81, 82, 85, 87, 84, 91, 92, 97, 94, 93, 99. Can someone please help me? The truck idles at 500 rpm.

 

This is the list I found. http://www.troublecodes.net/Ford/ According to this, everything but your license plate had gone bad. Thats usually an indication of a computer problem because a bad ECU will blame anything but itself, but I'm no EFI mechanic. I had an ECU go bad a few months ago on my 94 460. It would run, but very badly, as it was running way rich, which is fine because gas is cheap in the summer. I took it to a shop that started with the distributor, which was also bad. Helped but didn't fix, so we went to the computer and that did it. If a set of plugs or a MAP sensor doesn't do it, I'd take it to a trusted shop. This kind of diagnostic work is worth the dough if it saves the time and heartache.

 

where would I find the MAF on this model

 

Your truck does not use Mass Airflow (MAF), it uses Speed Density (SD). Therefore no MAF meter.

 

The SD uses a MAP sensor , located on the firewall on the passenger side. It is black and squarish, it will have a vacuum line and wiring harness plugged into it.

 

I tested the electric part of the MAP. the left lead shows 3 volts instead of 5 volts, which points to the unit not getting the proper 5 volt operating voltage, the right lead show 12 volts. So, I think that this means that the computer isn't allowing the necessary power to run the MAP. I did not check pressure no gauge or the hz.no hz meter. Any response other than the problem being the ECU.

 

i made an error in the numbers. .03 volts

 

What are you using as a ground reference? No way the Signal Return lead is a higher value than VREF unless something really bad happened.

 

I used the negative post of the battery. I do not have a hz reading meter so I can't test the rise and fall of the signal. what I have checked is if the sensor is receiving the correct voltage to operate. The left connector when hooked to a voltage meter is suppose to read 5 volts during koeo. red probe to connector black to ground, then the other outer connector is test by black probe to connector and red to positive side of battery. this is the site I used to. I got a .03 reading on the first voltage test and a 12 volt reading on the other connection. so I am assuming that the ecm isn't supplying enough voltage to power the sensor. Part 2 -Ford MAP Sensor Test (4.9L, 5.0L, 5.8L).

 

That code 19 with it backed up with all those other codes (I didn't check each and every one but enough of them I'd think) looks to suggest multiple sensors failure sharing a common circuit and backed up with that reading of ".03 volts".

All tend suggest to me the GRY-Red wire might be damaged, it might be pinched and or burnt/melted allowing it be partially ground out or cut most way through at some point. I lean toward ground out though.

 

All readings are typically referenced to the negative side of the battery or a GOOD chassis ground. I looked at the info in the link you posted. Very odd way to determine if the MAP sensor is open. That right lead on the MAP sensor, referenced as #3 in that URL, is your Signal Return to the PCM.

The VREF voltage for the MAP sensor comes from pin 26 on the PCM:


Either VREF is bad out of the PCM or something is loading it down.

 

Take a look:

61: Operator error, did you warm up the engine/transmission before running the KOEO tests?

66: Operator error, did you warm up the engine/transmission before running the KOEO tests?

22: MAP/BP sensor out of self test range. <---- that is a problem, but if VREF is low there is your root cause.

63: TPS circuit below minimum 0.6 volts. <---- that is a problem, but if VREF is low there is your root cause.

64: Operator error, did you warm up the engine/transmission before running the KOEO tests?

31: EVP circuit below minimum voltage of 0.24 volts.<---- that is a problem, but if VREF is low there is your root cause.

67: Neutral safety circuit failure. Was the truck in Park?

19: Failure in EEC internal voltage.<----There is your root cause. Perhaps a sensor is pulling down the voltage or a chaffed wire is a high resistance short, causing the voltage drop problem? My Ford Service manual states to replace the PCM....

81: Air management 2 circuit failure (AM2/TAD). Are the TAB/TAD solenoids connected electrically?

82: Air management 1 circuit failure (AM1/TAB). Are the TAB/TAD solenoids connected electrically?

85: Canister Purge Solenoid circuit failure. is the CANP solenoid connected electrically?

87: Fuel pump primary circuit failure. When the FP relay was activated by the EEC, voltage was not detected on the control circuit.

84: EGR Vacuum Solenoid circuit failure. is the EVR connected electrically?

91: Shift solenoid 1 circuit failure (E4OD).

92: Shift solenoid 2 circuit failure (E4OD).

97: Overdrive cancel indicator light circuit failure (E4OD).

94: Converter clutch solenoid circuit failure (E4OD).

93: Coast clutch solenoid circuit failure (E4OD).

99: Electronic pressure control circuit failure (E4OD).

 

it is beginning to get beyond my experience. Tracing grey/red line better known as VREF 26 seems impossible everything is bundled. There is a place on the drivers side firewall were all the wiring seems to separate going through a disk shaped wiring separator of some sort. Question about pcm's location. center of truck behind dash? can it be taken out without disconnecting . no i did not heat up the truck reference 61 66 64 the truck was in park 81 82 85 unknown at this time.

 

In the beginning, the positive cable leading from the battery got hot!! and the truck would not crank. I changed out the battery. It fired the motor for two days and then the truck would not crank. The old battery showed 12.7 after charging but it would not start the truck start and less than 12 volts recharging is now in process. I think the voltage regulator is bad any ideas can this be the short.

 

It's located behind the driver side kick panel. Here is a shot from the engine compartment:


On your '91 it may be removed inside the truck. I know my '92 and later trucks it is removed from the engine side.