Oops, removing post, was meant for somewhere else.

 

Just say no.

It's annoying that these capacitors are failing after 25 years, but replacing them, or even simply replacing the PCM with a rebuilt one, is much easier and cost-effective vs. a carb swap.

 

Sorry, posted this in the wrong thread.....

 

Fuel Injection Technical Library » EEC Computers

 

I've got a never-ending misfire on cylinders 2/3/6/7.

I've put several remanufactured PCMs in (two each from O'Reilly's and Autozone), and had one working like a song for a couple of weeks. Drove through some heavy rain and then misfires popped up again.

I've put another remanufactured in after that one, no luck. Same misfire.

I put in a junkyard PCM with matching codes (got lucky), no luck.

I put in a separate near matching PCM (junkyard), same misfire.

On my matching numbers junkyard PCM, I inspected the board, had some very lightly bulging capacitors, so I replaced all three with appropriate new capacitors, but no luck. Still misfiring.

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I'm a bit stumped, because one of the remanufactured PCMs worked perfectly for a few weeks. Drove my F-250 400 miles without a single issue.

Before the PCM replacement, I traced every little detail, and then paid a reputable mechanic to diagnose. He confirmed my suspicion that the PCM was bad.

I've tried wiggling the pigtail a bit to see if I might have a short there. No change in engine performance. I've disassembled my PCM pigtail and inspected everything - it was clean and in great shape.

I've tried a jumper wire from pin 59 (which sends ground to 2/3/6/7) to the white wire on cylinder 6, no change in things.

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So here's where my brain is currently at:

Option 1: buy another remanufactured PCM from an auto parts store where it can be returned (just in case), and try my luck once more. Or do any forum members have a KNOWN GOOD F5TF BAN1 PCM they want to sell me for $100?
Option 2: Could there be some other component on the board that is not working (the board was super clean and in great shape by visual inspection)
Option 3: My spark plug wires are not using wire separators. I've read that some are best crossing perpendicularly to others. I doubt this is a fix, because she ran so well for 400 miles.
Option 4: What else could possibly be the cause?

This is my thread with more history. Believe me, I'm pretty confident that the problem is at or near the PCM side of the story. I can't imagine I missed something else, but would appreciate any one's great thinking to help me. I bought the truck with this problem in November and have barely gotten to enjoy it so far.

Thanks for reading!

 

The PCM plugs pin #59 is either spread or it is pushed back when it is plugged into the PCM.
Just use a BOB with the BOB extension cable and check pin #59.
If it dose not have a miss with the BOB then you know it is the PCM plug #59 that is bad.

Or you could use a EEC-IV recorder and record pin #59 as you drive.
Else it will show a bad PCM.

Any shop that works on the EEC-IV systems should have a BOB and EEC-IV recorder.

 

Ok, you all talked me into it.

I ordered my capacitors last night. Had to order from 2 different places to get all the same brand (Panasonic) of all 3 capacitors. I haven't pulled my PCM yet, so I don't know if I needed 2 or 3, but I know how my luck runs, so better to be prepared.

I'll post pics after I get the computer removed.

 

Ok, removed my computer and replaced the capacitors this weekend. I was suspicious that my computer may have had the capacitors replaced in the past since they weren't the blue ones everyone else has shown, mine were a chocolate brown color. Maybe they changed to a different one in the later years, but I don't know for certain.
Before I attempted to remove my computer I had watched a YT video and the person showed that they were able to remove it from the inside by removing the kick panel, then one bolt and bracket, and then sliding the computer out past the parking brake assembly. Well.....no such luck in my 96 F350, the computer was completely trapped behind the PB assembly and some type of mounting bracket. So...I had to do it the other way from under the hood, which was a significantly bigger PITA since I had to remove a bunch of hardware for the inner wheel well liner and then push down the plastic liner while trying to fish out the computer. Kinda reminded me of aircraft I worked on years ago where it made me wonder if some engineer stood there and figured out a way to make it way more complicated than it ever needed to be to remove something simple.
Anyway....I got the computer out, checked the p/n @subford gave me, and that all matched up.
Here's the pics I took of the whole operation. In the first pic, the capacitors look fine, but there is some corrosion on a device in front of one of the caps on the right side of the pic. I don't know what caused it, but I couldn't find anything obvious. I used some alcohol and an acid brush to scrub it off. Then I moved to replacing the caps one by one. In my computer I had 2 of the 47uf caps and 1 10uf cap.

Here's the after pic. The glossy stuff you see around the repaired areas is the conformal coating I applied after the repairs. I did clean all the areas with alcohol and brush to get off the flux and such from the new solder before putting the conformal coating on. I put the computer back in the truck and it seemed to run just fine, and no CE lights.


Thanks to everyone else who supplied info for this repair.

 

You got lucky the PCB was not eaten up by capacitor leakage. I just got a 92 F250 parts truck sunday, found the ECU had bad damage to PCB while replacing the caps. Well that ECU will not boot up and run truck at all still. It not sending out 5V ref to sensors and no diagnostic modes work. Going to recheck if more traces are bad which is most likely.

As a side note, I put in a ECU I had laying around for a 5.8L V8 engine. The I6 engine did run but not good( missing 2 cylinders really confused the V8 ECU). I then tried another ECU, It ran the engine fine till I put the SPOUT back in and it stalled. I found out that ECU was for a 4.0L V6 with EDIS ignition hence reason the ignition failed when SPOUT back in. Final test was with my backup ECU for my 89 F250 I6 engine. Engine ran good with SPOUT in. Now I got a good spare engine

 

I was ok with my board not being eaten up. My truck was well taken care of before I got it about 7 months ago, so I was hoping that if there had been some type of computer issue previously it would've been addressed. I have no way of knowing if I have the original computer or if it's been repaired/replaced previously. When I saw the condition of the computer inside, I almost passed on replacing the caps since they seemed to be in excellent condition, but given my intended use for the truck (and my usual run of luck) I decided not to take any chances. If they were the original caps I didn't want to take the chance with them being almost 30 years old.