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Weak cylinder/injector #7

1995 f150 5.8 262k

So I just replaced the distributor for a random stall issue, which seems fixed, and now I’m getting a code for weak injector #7 from the cylinder balance test. It only failed the first test and passed the second. I know this isn’t the best way to truly test the cylinders/injectors but it’s what I have.

No KOEO/KOER codes and just a slight shake sometimes at idle but RPM never falls below 5k. The spark plugs and wires were replaced about 5/6 years ago.

And the fuel injectors…yeah those have never been cleaned for the life of the truck.

I was thinking of pulling the spark plug and seeing how it looks and maybe cleaning the fuel injectors with the sea foam in the fuel rail method, but I’m worried about knocking gunk loose and causing myself more issues.

What do you guys think?
 

dustybumpers

don't play well w others
5.8 is a bugger to get not to cross fire between cyl 7 & 8.
you need to buy a new high pro set of wires. put Motocraft plugs back in, as the 5.8 don't like anything else.
Me knowing this I did just the opposite od what I'm telling you on 2 of my trucks recently. Used stock type wires and ngk plugs. The 5.8 missed so bad I thought the transmission was taking a poo, converter lockup.
I had a friend suggest powerbrake it in reverse, and sure enough high speed miss.

My 94 ho 5.0 uses the 5.8 firing order, so same problem. new plugs, new wires, and that one new motor.
high speed miss.
Soooooo
long story, I'll screenshot the wires you need from rockauto, and pick up Motocraft plugs

make sure to separate the wires with the separators provided, may even pick up another pack at the local auto supply.
dielectric grease on both ends, and cruise on!
 

dustybumpers

don't play well w others
I looked it up as a 94 5.8. They all are pretty much the same.
The chart says what whire goes where
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dustybumpers

don't play well w others
Like I stated, the more you keep them separated, the better they do. This is the ho5.0
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Wow that looks clean!! I definitely don’t have separators like that, I think I’ve lost half of them. I’ll make sure to get them on with the new wires though.
 

dustybumpers

don't play well w others
1 set comes with the wires. You can buy them at advance, autozone, etc

Pay special attention to #4, which in my bundle you see i actually put a piece of wire loom on to go under the plenum, and 7-8. Those are the trouble makers. Look at your firing order and you will see why.
13726548.



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dustybumpers

don't play well w others
The 90 5.8 isn't so pretty, because of emissions equipment, but it is still possible to seperate
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heavydoc

Instigator
Staff member
1,969
38
WNC
Cut the tails of the dang zip ties!
 

dustybumpers

don't play well w others
Lmao. Posted that 5 years ago for you when I redid the exhaust manifolds and emissions, posted it today for the fresh wires. left them zip ties long like that just for you.

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fatherdoug

Tonto Papadapolous
Lmao. Posted that 5 years ago for you when I redid the exhaust manifolds and emissions, posted it today for the fresh wires. left them zip ties long like that just for you.

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I love the things you do to make people happy. :rofl:
 

dustybumpers

don't play well w others
This should make you happy then father doug. Restrorodding my 89 f 350
Superduty axles, and a bunch of other goodies.
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fatherdoug

Tonto Papadapolous
I've always secretly wanted to do that to my '78. Old school look with the modern necessities. And yes, at my age, they are necessities. How is the fit?
 

dustybumpers

don't play well w others
Some things are available, some im building, fabricating.
It's an interesting project, lots of research.
Currently thinking about abs brakes all the way around, even though I have already run the lines to everything but the master cyl.
What's the famous saying....
Everything is subject to change

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That is a whole other level of work, maybe I’ll get there some day!

What is your opinion on anti seize on the spark plugs or not?
 

Fellro

Moderator
Staff member
My opinion here in rust country is yes, use it. Also use dielectric grease on the plug wire boots.
 

fatherdoug

Tonto Papadapolous
I'm guessing antiseize on sparkplugs is not a good idea. Antiseize can change the torque value of the plug, and the nickel plating on the plug acts as antiseize. Somebody can verify my theory on that. If I am wrong, I'll just go back to my hole and stay there. :D

^^^Guess I'll go back to my hole, Roger.
 

Fellro

Moderator
Staff member
I have heard the arguments but my experience is it helps for getting them out the next time. I have also had cars come in with the plugs so rusted up the center ceramic blew out... Around here, if you don't do something, the plugs will get rusted up so bad they are difficult to remove. Many bolts are the same thing, the plating doesn't hold up to the road salts. Now in Florida it may not be as much of an issue.

Never heard the nickel plating would help as antisieze, just corrosion inhibitor. As far as torque, shouldn't really be an issue as the spark plugs don't hold a load like say a head bolt.
 

dustybumpers

don't play well w others
I have done both. Not a fan of gooping on the antiseeze, but a thin coat should be fine. Absolutely on the dielectric grease on both ends of the wires

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New plugs and wires are in! I used a very small amount of anti seize.

I’ll drive her for a few days and she how she feels, run the balance test and then I’ll post again.

Thanks for the help!
 
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