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Part one is a little better:
https://www.youtube.com/watch?v=MQ4ft54bpfM

I guess it could be possible that I'm on the front end of a valve failing, I've just never had one fail "some of the time" like the way this one is. In my limited experience, it has always been a light switch thing that tended not to fix itself once it failed.

Thanks for the suggestion though!
 

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Discussion Starter #143
So I Had some time Tuesday night to get after this the best that I could. I cleaned the firewall, PCM, Coil Pack, and Alternator connectors. I also gave the power distribution box a good once over. None of which showed any signs of corrision, and honestly the harness isn't brittle or falling apart even though it is 18 years old and has 185k miles worth of heat cycles on it.

However, the results of the above work reduced the amount and frequency that this thing misfires. So at this point, I believe that I am dealing with a wiring issue internal to the harness itself. Since I'm not finding any NOS harnesses, I'm left with tearing into this piece by piece (Boo!). But it is at least more derivable at this point.

I plan to start on the coil pack loom as I have time since it is a bit more accessible than the injector loom. And again, the injector loom looked pretty dang good when I swapped out the injectors.

I was kind of hoping everyone would say "Oh yeah, X tends to fail routinely causing your issue!". But the deeper I search the more comments about a bad engine loom than I would have thought which surprises me for as new of a vehicle as this is.

I'll keep this thread updated as I find stuff out, but it'll be a while.
 

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Sub'd for the diagnosis.

I'm running a 98 OBDII 5.0 from an explorer in my early bronco with a ZF5. It too has an intermittent miss that has been difficult to nail down. No codes, but it does seem to be tied to the computer going closed loop once the engine is warmed up. Interested to see how this shakes out.

Do you have a video of the miss?
 

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Would it be a bit less down time and fussy to get a good wiring harness from the JY and go through that? Then swap them out when you have some free time.
 

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*knock on wood, this kind of thing scares me (although mine is a 94) I am terrified of 90's ford wiring. "Hey lets put a 36 pin connector on the rear wiper and draw the main 12v from the transfer case"
 

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Discussion Starter #148
Do you have a video of the miss?
Nope, I'll try to grab one this weekend as we're heading out to wheel a bit so I'll have some road time ahead of me.

Would it be a bit less down time and fussy to get a good wiring harness from the JY and go through that? Then swap them out when you have some free time.
Very likely the route I'll go at some point. I'll try to take the easy road first knowing full well that it never works out for me in the end :laughing:

But, this is one of the nicer wiring harness (condition wise) that I have seen. So it it worthwhile to try to save as much of it as I can. The clips are in good shape, wires aren't brittle, etc.

*knock on wood, this kind of thing scares me (although mine is a 94) I am terrified of 90's ford wiring. "Hey lets put a 36 pin connector on the rear wiper and draw the main 12v from the transfer case"
It seems like Ford cheaped out on the late 90's early 00's wiring on the trucks/suv's. I've had a couple of the RBV's now from that time period and all of them seem to have some odd wiring kinks, where the early to mid 90's stuff just kept on ticking even thought the harnesses looked more jank.

If it wasn't for the emissions aspect of this, I would just run a stand alone and be done with it.
 

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It seems like Ford cheaped out on the late 90's early 00's wiring on the trucks/suv's. I've had a couple of the RBV's now from that time period and all of them seem to have some odd wiring kinks, where the early to mid 90's stuff just kept on ticking even thought the harnesses looked more jank.

If it wasn't for the emissions aspect of this, I would just run a stand alone and be done with it.
do you have an EVTM for your year truck? If not, get on ebay and pick one up. for as old as it is, probably won't be much. I have one for the explorer, the ranger body, and the explorer the engine in the ranger came out of and still didn't spend 100 bucks on all of them
 

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Discussion Starter #150
do you have an EVTM for your year truck? If not, get on ebay and pick one up. for as old as it is, probably won't be much. I have one for the explorer, the ranger body, and the explorer the engine in the ranger came out of and still didn't spend 100 bucks on all of them
Yup! One of the first things I buy when I pick up a project I plan to hold onto is a Paper Copy of the Factory Service Manual (including the wiring diagram books if separate). I often throw them in the the truck before our big long trips too as it's save my butt more than one time when out in the boonies trying to diagnosis something.
 

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Discussion Starter #151
Update for the week. Still missing, but I think it is getting better in that it is less severe and less frequent. But it might be a bit of wishful thinking on my part.

Cilffs:
- Swapped CPS and checked the wires going to it - No change
- Played around with grounds to the coil packs, no change though I am 100% certain that the grounds are good now
- Popped the PCM apart to take a peek, all looks good in there (nothing burnt, no popped capacitors)
- Swapped out the Alternator as it was on the way out - no change but it is charging better at least :rolleyes:
- Pulled apart the easily accessible harness going to the coil packs, looks good there.

So when I work up the motivation, I'll pull the upper intake off and dig into the fuel injector harness to see if anything is awry there, but I'm not really holding my breath at this point.

it's the darnedest thing though, went wheeling last weekend. It missed on the 2.5 hour drive down to the park. Didn't skip a beat the entire time we wheeled all day, then missed on the 2.5 hour drive back home. I'm just flat out stumped and not entirely convinced it is the harness at this point, but don't really know what else it could be.

Do you have a video of the miss?
The only way I can get this thing to not miss is to pull out the camera apparently :rolleyes: But I keep trying to catch it while it is behaving poorly.
 

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I'm waiting for you to figure this out so I can see if I can implement the solution on my 4.0. I've had a slight blip at highway speeds (continuous highway RPM) ever since I swapped it in. It's mostly audible and hasn't seemed to affect performance, so I've just rolled with it forever.

Thanks for doing all of the legwork. :flipoff2:

Edit: I should add that I go through plug wires fairly frequently. 3 out of my 4 trips to Moab have required a wire swap upon arrival. When I have the performance drop, I know it's time to swap out wires. It happens so much that I keep a box of spares in my toolbox. I've replaced my coil and all that jazz - nothing has seemed to remove the highway blip.
 

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*really dumb innernet question


Have you tried just Seafoaming the shit out of it? Don't wanna get your hopes up, but it solved my random 4.0 miss a few years back.
 

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Seafoam scares me. I added some to my oil in my 3.0 and a week later all of the garbage that it freed ended up plugging my oil pump. Lost pressure and killed the engine. That's what initiated the 4.0 swap.

I suppose I could play it safe and keep it on the fuel/intake side of things.
 

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I suppose I could play it safe and keep it on the fuel/intake side of things.
This. I'd never add something like seafoam to my oil for the reason you stated.
 

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Discussion Starter #157
I'm waiting for you to figure this out so I can see if I can implement the solution on my 4.0. I've had a slight blip at highway speeds (continuous highway RPM) ever since I swapped it in. It's mostly audible and hasn't seemed to affect performance, so I've just rolled with it forever.

Thanks for doing all of the legwork. :flipoff2:
Don't hold your breath :flipoff2:

The 4.0 in the '94 Ranger would have an odd miss when cold that would go away once it warmed up. I always suspected it was EGR related, but never looked into it as it never bothered me that much.

Buuutt.. What you're describing sounds EGR related, and that system is getting old enough to possibly warrant looking at. Especially the DPFE which mounts to the back of the intake.

I'd just rock out and not worry about it unless it gets worse.

The spark plug/wire thing is a bit odd though...

*really dumb innernet question

Have you tried just Seafoaming the shit out of it? Don't wanna get your hopes up, but it solved my random 4.0 miss a few years back.
Not to mine I haven't. When I had the intake off, I stuck a camera down in the lower intake and the upper intake half. I can't stress how clean this motor is. If I didn't know better, I would swear that it is not original to the truck given how tight and clean everything is... (now watch it window the block on the way home from work this afternoon)....
 

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Seafoam scares me. I added some to my oil in my 3.0 and a week later all of the garbage that it freed ended up plugging my oil pump. Lost pressure and killed the engine. That's what initiated the 4.0 swap.

I suppose I could play it safe and keep it on the fuel/intake side of things.
I don't ever pour anything in my crank case but quality motor oil.

I know a bunch of old timers who would dump gasoline in there for 10 minutes to "clean her out". Fuck that, oil has detergents. If it's not doing it's job you're a Pennzoil loving fool.

Running the stuff through your intake doesn't hurt a thing. I never noticed a difference when I tried it but apparently a lot of people swear by it. Probably because I run good oil, don't overheat my shit, and change it on time, and change regular tune up items when I should.

That doesn't mean it's not cleaning valves on someone's engine though.
 

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On a direct injected engine, I'd see the benefits of seafoam for sure - since there's no gasoline washing the EGR crap off the valves with each engine revolution.

I did seafoam on the intake on my 5.3L years ago and while it smoked like crazy, it didn't see to run any better or worse after.
 

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Discussion Starter #160
Still fighting the miss-fire, but we did manage to go wheeling a couple of weeks back.

3rd ORT at Flat Nasty 8-12-17

The first trip out in the Merc with both kids in tow was a success! So hopefully we can work on getting out more frequently than we have been. We spend the better part of the day on the “Tourist” loop in consideration for the younger folks that were with us, but we still managed to play on a few things here and there:















 
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