Hey guys.

Have recently purchased a '91 F150 Custom with a 5.0, 4x4 with 5 speed. It really needs some love shown it and I am willing to give it a try.

My problem is, I've been reading a lot on the forum here and I am no longer sure of a couple of things. I think its 'speed density' since I can find NOTHING that looks MAF like. And I am going with it giving me 2 digit codes since that is the only sequence of numbers that make sense from all the blinking.

Pulling codes, I get KOEO codes 21, 24 with KOER I get 21,41,18, 25. From what I can find I gather 41 is System Lean, Fuel Control. Could that be because the PO cut the cats out and just shoved some flex tubing into the cuts (kind of) and ran some exhaust pipe to 2 small mufflers and bailing wired the whole thing up? Could this be causing the 02 sensor to freak? And then 18.....check base timing and advance function......Im waiting for the timing light I ordered to get here to check the timing. Its the 'advance function' that has me stymied. Is that related to the 'SPOUT'? And if so, just how does one check it for sure? Are codes 41, 18 the ones I should be most concerned with at this point in time?

I've replaced the plugs and rotor and distributor caps, even plugged the #3 plug wire back onto the plug. Oh and all the plugs were only in 2 finger tight. Im having to budget in what I can get so plug wires are next since there are 2 different types on it, I think one is even only a 7mm wire.

Thanks for reading this. I hope I haven't been to incoherent

 

You are correct, your truck is Speed Density that uses a MAP sensor located on the firewall.

You are correct. A 1988 model year truck will display 2 digit codes.


What about stored codes from Continuous Memory?


If there is enough of a leak from the cobbled exhaust the O2 sensor could be sensing extra air.

KOER Code 18: SPOUT circuit open



Verify the SPOUT plug is installed. It's located near the distributor.


I would be concerned about Code 21 ECT out of self test range 0.3 to 3.7 volts if the truck was really fully warmed up before running the KOER tests. Same for KOEO Code 24.

 

Rla covered everything. But, just to add my $.02. You stated it's a 5 speed, automatically makes it speed density for a truck. Nobody that I have heard of or talked to has EVER seen a MAF manual truck before 96. So rule of thumb, manual equals speed density.

 

Welcome to FTE Deadulus! Make it easy on yourself to read codes, grab one of these guys:
I've never used it but I've seen it recommended on here several times and it seems like it would work well.

 

RLA, I can't remember if it was completely warm when I did the codes. Will redo it. Can the SPOUT plug go bad? There was no difference in the way the truck ran when it was in or when I had it out. I think there may be a short or loose connection on the coolant sensor, when I go over a bump it goes whacky and stops working for awhile. Or and there is plenty of exhaust leak, I took the pipes off since there was no real use for them being hanging there with the 2 inch gap between the flex pipe and manifold. Finally....stored codes? There was no battery in the truck for a month before I bought it. Would that affect the stored codes?

Thank you for the replies! I will probably be asking a LOT more questions in the future.

 

On the coolant sensor:
There are two, one for the gauge, one for the computer. The one for the gauge is usually a single wire, the one for the computer is two wires. That's the case on my '90 7.5, so not sure if the same for your 5.0

 

The SPOUT is a simple shorting plug. It completes the circuit between the computer and the Ignition Control Module (ICM). I suppose it could go bad or the connection is bad. Measure the SPOUT plug with a meter. It should be a short/very low resistance.



There are two "coolant sensors". One is the Engine Coolant temperature sensor (ECT) that provides feedback to the computer. The other is used for the temperature gauge in the dash. Two completely different sensors and functions.


Yes it would, you would get System Pass Code 11 if there are no stored codes. FYI...there are two parts to the Key On Engine Off tests/code display procedure. The first are the Key On Engine Off tests. If there are no test failures you will get System Pass Code 11. Then there is a separator flash that indicates the Stored Code (aka Continuous Memory) display is starting. If there are no stored codes you will receive System Pass Code 11.

If you remove the code reader/jumper before the KOEO and CM codes are finished displaying you will clear any stored codes in Continuous Memory.

 

Good to know. Thank you.