Thanks ArdWrknTrk and Frankin2!

comtb: While I am uploading a couple of photos, comtb could you describe the symptoms you were having which made you suspect that you had a bad EEC-IV PCM?

 

Can anyone tell me if this is a replacement PCM from the numbers on it? It looks too pristine to me to be 20 years old.

 

More photos.

 

My symptoms have been a multiple misses or stumbles or hesitations or bucking at around 1500 rpms while lightly accelerating.

The problem is intermittent.

Turning off the overdrive which increases the rpm's eliminates or reduces the symptoms.

I just replaced the fuel pump and frame rail driver's side fuel filter so fuel should not be an issue.

The PCM and its capacitors look good to me.

If the PCM also looks good to you guys, I think I will just DeoxIT D5 with micro Qtips and DeoxIT Gold G5 the male and female bullet connectors and reinstall the PCM without capacitor replacement (first rule is: "Do no harm."), and monitor my vehicle for proper sensor working since I just bought a New Generation STAR scan tool with the appropriate Data Link Connector cord and Black Diagnostic Card for the vehicle.

 

I took photos but they are not very good. Tried to upload, but after 9 min. site tells me - wrong file or format. They are JPEG. I will try again. Reman cpu fixed the fuel pumps running all the time and it runs better but not 100%. The new Standard brand EVR is no good and I'm getting a code 558. Two more trys at upload = ng

 

Slomoe: The site will upload jpeg but there is a size limit, so I have to first edit or export my pics to a lower resolution i.e., fewer pixels ups and across. Then they upload fine. No reason to believe it will be better, but out for a drive. Be back soon...

 

The reman cpu I got from Rock - Cardone brand, does not have the original ford label. It only has a Cardone P/N label on the side.

 

Still have same symptoms.
I am still learning how to use the NGS, but it seems to have passed the general diagnostic checks which if there was a problem would point to a pinpoint test to perform. So...

 

I see 1995 date codes on many of the components, so I'd say it was manufactured in 1995. In high-volume electronics manufacturing, components don't sit in stock very long. Many shipments coming in to a schedule, and parts are FIFO'd through stock. The closer to JIT, the lower the total mfg. cost.

 

Some problems are very hard to find. I wish I had the tools to monitor what's going on in the cylinder, after all, this other stuff is just support to what's important, the proper combustion of the fuel at the correct time. I think the guys with a lot of experience can look at the time the injectors are on, and figure out what's happening fuel wise, and if you had a machine to look at the waveform of the spark in each cylinder, you could make sure you have the proper spark.

I just went through this very thing with a little 2.9 v6 86 ranger someone gave me. It would start right up, had lots of power, and the engine was clean, did not burn a drop of oil. But when I got it, it had a terribly rough idle. I thought ok, full tune up. Didn't fix it.

New fuel injectors(one plug was damp). Didn't fix it.

No codes.

Messed with the IAC(the idle was unstable). Took the IAC completely out, opened the butterfly up and recalibrated the TPS. Didn't help it. What did help it was raising the idle speed. Force it to about 800-1000, it would smooth right out.

I messed with this thing on and off for about 3 years, driving it all the while. It was driveable, but you had to make sure you slipped the clutch leaving a stoplight or it would tend to stall. I accidentally fixed it about 3 months ago. I was under the hood looking around after a oil change, and noticed there was a ground wire bolted to the coil bracket, going through a harness split loom, and bolted to the aluminum intake. It didn't look that good on the coil side. So I took it off, cleaned up both ends, and put it back on, not really still pursuing the idle problem. I could not believe it, it smoothed right out after starting it up. I am assuming my problem all along was a weak spark.

 

Torky2 and All: So since many of the components are 1995, do you believe that it is the original PCM? And if so, do you believe that I should just replace the capacitors for good measure regardless of the fact that the don't appear to be leaking, don't appear to be bulging and their solder connections look good, at least to me?

 

Franklin2: I am going to really look hard at stuff like what you mentioned. See this:

from:

https://www.ford-trucks.com/forums/8...nder-load.html

My engine is not muddy, not greasy (at least on top) but it has 20-years of dust. Any suggestions on how I clean it without hurting the electrical components?

And BTW, there is a picture of Y2KW57's cab in the 7.3 forum with an oscilloscope in addition to the NGS!

And yes, the engine is passing its KOER and KOEO diagnostic routines on my new to me NGS. Although I can't seem to do the Cyl. Bal. test right.

 

Tim, with all the 1995 date codes on the parts, it is a 1995-manufactured PCM. Now whether it was your truck's original PCM, or someone else's 1995 PCM, no way I could say.

With a visual not finding any problems with the caps, I would not replace them.

The link to the cylinder #7 - #8 crossfire, that is only relevant to a 302. The 351 has a different firing order and is not prone to the 7 - 8 crossfire problem. About that link... a sparkplug wire crossing another at an angle is NOT a problem, unless the insulation is going and results in an arc from one to the other. The problem with cross-firing is the pulse in one spark plug wire gets induced into another wire because they run parallel and close together for too much of a distance (mutual inductive coupling). A common way to reduce that is to separate the wires, and if they need to physically cross somewhere, do so at/near a 90 degree angle between the two offending wires.

Your miss at around 1500 RPM... that is in the RPM range where EGR starts to work. May be a coincidence, or?

For COP (Coil On Plug) engines like the 4.6 and 5.4L, light throttle around that RPM is a common area for COPS to exhibit problems as EGR and mixture are finely balance there. That might/might not be a possible clue, maybe your spark is weak? Franklin mentioned that in his problem he related. At least you could verify that you have good fat juicy spark at idle, then get someone (someone you trust!) to run up idle to 1500 RPM while you check spark again. True, it won't be under load, but that might be the best that can be done with that.

 

20 year old electrolytic caps will break down just sitting on the shelf (ask me how I know...)

I would replace them as a matter of course.

The 7-8 inductive misfire is an issue with 460's as well.
Good (shielded) wires help.
Running them apart from each other is important.

 

ArdWrknTrk: I just went out and looked at the wires and there was a little rubber on the surface of a spark plug wire abraded? or from arcing on one wire where it touches another. Do you have a recommendation for wires? And I am now looking up 5.8L spark plug wire routing. And OK, I will ask how do you know?


Torky2: I am not now getting and there are not any stored DTC codes. However I could have sworn that the dash light was flashing 3-4 but I was told that my EEC-IV does not flash dash two digit codes, only three digit codes. So last month I threw a part at the truck in the form of a new EGR sensor, but I need to learn to clean the EGR valve to further investigate that possibility. The miss starts at 1500 rpm. But I can make it happen at any rpm (e.g., 2500 - 3000) if I accelerate hard or pull a load up a hill. Only increasing rpm by turning OD off or downshifting will eliminate or reduce it when it is happening.

And Happy Easter to All!