Had my 91 5.8 e4od full of tools and my welder today and got a check engine light for the first time in this truck.

It would come on mostly at low throttle and then shut off when getting on the gas to pass or whatever and would also turn off with no throttle at say a stop sign.
Anyway, no big deal, got home and checked for codes...
This is where I'm confused,
After putting the jumpers on the cel would be lit before turning the key and then go out after turning the key on and no codes.

So I unplugged the jumper to the battery and left the small jumper and tried it ,turned the key and got 2 slow flashes, 2 quick flashes, 1 slow flash , 3 quick flashes, 3 quick flashes ,3 quick flashes and 3 quick flashes.

This is the first 88-91 (had numerous 92-96 fords) I have owned and checked for codes, so I'm wondering what's going on?!

 

I could be wrong but I believe that OBD 1 has no memory, in my experience on my 92 the only way I have ever retrieved a code (with my scanner) has been when the light is on and stays on. Every time I checked mine after a random light that came on / went off the scanner said no codes. I have never tried the jumper method so I can't help you there. Next time you are driving and it stays on pull into autozone, leave it running and have them pull the code. They do it for free

 

They do have a memory for stores codes. And autozone can't pull codes on anything older than 97. I tried the jumper method also but I got confused so I bought a code reader from amazon for 35 dollars.

 

What I'm confused about is why I couldn't get codes with the jumpers hooked up and then did with the small jumper only!

 

Could have had a bad connection the first time. Or it wasn't hooked up right not saying that it was.

 

Something must be wrong with my truck then, if my cel is on and I shut the truck off, no codes. Although the only thing that has ever tripped a cel on mine so far is the EGR valve getting stuck in cold weather.

 

I would clean the TB/TPS and Air flow sensor... see if the CEL goes away..

 

You can't clean tps, it doesn't have maf in 91.

 

I would start by checking fuses and grounds and go from there.

 

So... what is the question? You got the codes, I don't know exactly how you hooked up the wires but the one jumper is fine. Two digit codes, looks like 11 and 33.