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Discussion Starter · #1 · (Edited)
Wanted to aware others that our 85-95 & 96 EEC-IV/EEC-V ECU's are now a common failure and will cause no start conditions, transmission shifting problems, and poor engine running conditions upon failure or early failure. In the past "archives of FSB" we usually ruled ECU failure to be a very rare problem our vehicles experienced. I believe that is untrue today due to the aging of the capacitors and further damages they can cause to the board once leaked of their acid. A capacitor doesn't have to leak out to be faulty either.

Tools: EEC-IV & EEC-V ECU Failure now is a Common Problem...
Capacitors: EEC-IV & EEC-V ECU Failure now is a Common Problem...


Pfun- FSB Member

When I find more good EEC-IV repair and diagnosis videos I will post them.
 

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ITs amazing what goes wrong when a cap leaks out. When 2 or 3 things arn't working properly I pull the EEC and take a look. Its easy to get to and inspect. I've been posting about this more and more. Glad to see somebody else is too.
 

· Man of endless projects
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it does even affect the EEC-V like my 96. and unfortunately Cardon reman are pretty poor and are getting harder to find certian versions. especially the 94-96 MAF E4OD.

I had to replace my 96 PCM because i had a failure causing injector 1 not to pulse. then i had to replace it again cause it would not read over a certain voltage for the MAF. both of these were remans. luckilly i have an OBD-II reader that made finsing these issues easier, because otherwise for most people this would be a real pain to find
 

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'92 Custom w/ '95 MAF 5.0 M/T, 33's, 4.10 LSD
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The capacitors in '90s PCM's were generally good for 15-20 years max, so they're all on borrowed time by now if they haven't been serviced. The degree of the problem does seem to vary by car maker, though, and presumably what capacitors they spec'd. I know Toyotas had it pretty bad, but I haven't seen it be a common thing on Mazdas, for example.
 

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‘95 Bronco XLT 5.0 E4OD, MAF, Pace Setter short tube headers
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ive been in this boat for about 4 yrs now. i chased problems forever and even had my transmission rebuilt (turned out for free since it didnt fix it), i have an issue where my torque converter erratically locks and unlocks at low rpm causing stalls, and a few times its stalled and lost all total power like the battery disconnected. after three years i found that i have leaked capacitors in in my eec. (95 5.0 maf e4od, WAY1) ive spent a year off and on looking for a replacement but ive about give up. way1 is about as rare as hens teeth so it seems. about to send mine to get repaired hopefully that will suffice. anybody on here done there own repair? where can you find replacement capacitors if you have?
 

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‘95 Bronco XLT 5.0 E4OD, MAF, Pace Setter short tube headers
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okay what about cleaning the acid leak, anybody got tips on that?
 
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· Moderator and Scrounger Extraordinaire
85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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an issue where my torque converter erratically locks and unlocks at low rpm causing stalls, and a few times its stalled and lost all total power like the battery disconnected.
Just FYI, the torque converter locks when its circuit is grounded. The wire that controls this in the main E4OD harness is purple with a yellow stripe. A toggle switch can be used to manually lock it, but there is no way to manually unlock it. Unless you cut that wire from the ECU and made it permanently manually operated. Wgich would suck.
 

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‘95 Bronco XLT 5.0 E4OD, MAF, Pace Setter short tube headers
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Just FYI, the torque converter locks when its circuit is grounded. The wire that controls this in the main E4OD harness is purple with a yellow stripe. A toggle switch can be used to manually lock it, but there is no way to manually unlock it. Unless you cut that wire from the ECU and made it permanently manually operated. Wgich would suck.
Yuuup
 
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· Moderator and Scrounger Extraordinaire
85 Bronco, 309ci I6 w/4bbl, np435, 4" lift, 37" Irok NDs, 4.56 w/ Detroit Locker and tru trac
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As for the topic at hand: us bullnose freaks have been dealing with it for a while now. My 85 was an EEC IV controlled carburetor. Many of those things quit working shortly after Y2K. Many have been retrofitted to Duraspark II and a normal carb. I still have the EEC IV box in my 85 but i couldnt tell you if it even has power to it. Mine was converted back to POINTS ignition. And it ran damn good. My wiring is so hacked that im afraid to cut any more out!
 

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1995 5.8, 2.5" Rough Country Lift, Extended RA's, 4.10's, 33" BFG's
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As for the topic at hand: us bullnose freaks have been dealing with it for a while now. My 85 was an EEC IV controlled carburetor. Many of those things quit working shortly after Y2K. Many have been retrofitted to Duraspark II and a normal carb. I still have the EEC IV box in my 85 but i couldnt tell you if it even has power to it. Mine was converted back to POINTS ignition. And it ran damn good. My wiring is so hacked that im afraid to cut any more out!
Many of those things quit working shortly after leaving the dealers lot. I worked at a Big A Auto Parts in the 80's and that system drove mechanics nuts.
 
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1995 5.8, 2.5" Rough Country Lift, Extended RA's, 4.10's, 33" BFG's
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Good thread. After my PCM disaster last summer I would suggest sending your unit in for repair/rebuild vs buying one outright especially if you have a 5.8 with factory MAF
 

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1996 XLT Sport
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Thanks for the info as always!
This was definitely part of my decision to go aftermarket EFI with a stand alone trans controller.
As much as I wanted to stay OEM PCM, I knew it was aging.
 

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So, I watched the aluminum capacitor vid, and now I know where the unit is, lol.

I've soldered wiring stuff before, but never on a board. The iron I have has kind of a fat tip on it, prob need a narrower one.
But, how difficult is this, has anybody here done it? If I were to proactively go ahead and replace the capacitors, what are the odds of ruining the board?
He also mentions using higher capacity capacitors. Is that adviseable?
 

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Yo Guns,
Following from seedpress who had some first time capacitor replacement issues:
"I finally pulled the computer and, sure enough, two of the electrolytic capacitors had leaked. Not only were they shot, but the leaked electrolyte had begun corroding some pins on one of the semiconductors. The computer board is covered with a conformal coating to protect it against moisture and contamination, but the electrolyte had also seeped under or through that coating and discolored the board in places.

First I cut out all three of the electrolytic capacitors, although only two of the three had leaked. Then I tried to clean the spilled electrolyte. To remove the corrosive electrolyte I had to strip off the conformal coating where I saw board discoloration. I tried to clean the affected areas with rubbing alcohol, dilute acetone (used for finger nail polish remover), and WD-40. Also, one logic IC (integrated circuit) had three pins that were corroded by the electrolyte. I tried as best as I could to clean them mechanically.

The two leaking capacitors were 47uF 16V, and the third a 10uF 63 volt. I didn't have these values on hand, but coincidentally I had just bought a hundred 22uFs with a 63V working voltage. So by paralleling two of the 22s I was able to get 44uFs, and in series I got an 11 uf. Electrolytic caps have a wide tolerance range anyway, so I hoped that would be good enough. The one problem was all the original caps were 105 C temperature, whereas my replacements are only 85 C. But my computer is behind the driver's kick panel, instead of in the engine compartment. So, I am hoping it will work, at least for a while.

It was a pain to replace the caps! First, I found it difficult to solder the new, "paralleled" capacitors to the printed circuit board. Then, I wasn't sure how many layers the board had -- it's easy to overheat and ruin underlying layers. Finally, some of the copper pads to which the new caps were being soldered were also very close to fine-pitched copper traces. My finished "repair" is a real mess! But it seems to be working.

After all this, the pump is no longer latching up in the run position, and the engine starts. The Bronco hasn't been driven on the road yet. So, I guess I'll see how that goes soon. I am planning to get a replacement computer pretty soon, because I don't trust the old one, especially with my "iffy" repairs.

I'm not proud of my fix-it project, therefore I'll leave the finished product to your imagination; however, if you ever look inside your own EEC, you might want to know what leaking caps look like, so here's the “before” picture of my leaking caps:

Passive circuit component Circuit component Resistor Hardware programmer Audio equipment
 

· Charlie don't surf..
'92 Ford Bronco XLT
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So, I watched the aluminum capacitor vid, and now I know where the unit is, lol.

I've soldered wiring stuff before, but never on a board. The iron I have has kind of a fat tip on it, prob need a narrower one.
But, how difficult is this, has anybody here done it? If I were to proactively go ahead and replace the capacitors, what are the odds of ruining the board?
He also mentions using higher capacity capacitors. Is that adviseable?
Great thread..Thanks @GetBent4x4, we've needed something like this for a while..maybe we should make it a sticky??

@Gunfixr, if you're going to give this a shot, I'd invest in a good soldering iron that has a wide selection of tips..I haven't tried it myself, but I do have a couple of spares that I could practice on, so it's worth giving it a try..

I don't think the higher voltage capacitors will cause a problem..
 
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