Trucks Diagnostic question

Wildlifer

Old Mossy Horns
The truck is a 97 f150 and the code is a cylinder 8 misfire. I am having a little trouble pinpointing the issue because the misfire is intermittent. It came on after a fairly long drive and I could feel the miss. Drove it a few miles the next day and no miss until the very end of the drive. I just took it by the part store to get the exact code pulled and no miss there or back. The plugs and wires have about 75K on them. I'm not sure if its the plug going bad or the coil. Any advise on diagnostic techniques or how to pin point this?
 

Hank

Old Mossy Horns
I would try a plug and a coil in the cylinder, if that cures it, then change all the plugs.
 

Dan in NC

Eight Pointer
Contributor
Tonite when "very dark" open hood with engine running. Last two times I had coil plug and wire issues, there was a greenish blue light glow around wires and coils. Also each time I had code of cylinder misfire it was wires or plugs. I changed both each time.
 

Wildlifer

Old Mossy Horns
I would try a plug and a coil in the cylinder, if that cures it, then change all the plugs.

Thinking about doing the plugs. I was under the idea that plugs wouldn't be intermittent. The coil is a coil pack not individuals, one pack for each side.
 

tarheelshooter

Twelve Pointer
Contributor
Got to be a 4.6 liter since it has wires and coil packs......only did this for one or two years. All the rest are coil on plugs like the 5.4 liter.
Since it is very intermittent and only happens under loads while driving I would be looking hard at the wires. The only good way to check it is with an oscilloscope and getting kv ramps and firing lines,but this will only help if it is active at the time. Most likely you have a wire arcing to the inside of the plug well and you will never see it. You can pull the wire out and visually inspect it for signs of arcing (white spots on the boot) or lightly mist it with soapy water or glass cleaner and see if it skips after reinstalling it. The coil pack on this one fires two cylinders so you will usually drop out two cylinders when it dies.

What kind of plugs did you put in?
You are basically way past due on them anyway,but definitely past due if they are non-platinum.
 

Wildlifer

Old Mossy Horns
It is the 4.6 my analog odometer broke awhile ago so it's my best estimate on the plugs. Ac delco wires, the best ones I could get and iridium plugs, the should be good for 100k. I can pull the wire and inspect, that helps with trying to eliminate the coil from the equation.
 

mekanizm

Old Mossy Horns
Contributor
I replaced the plugs on my '98 f150 just because it was due and it missed horribly after that. I then had to change the wires to eliminate the misses.
 
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Ldsoldier

Old Mossy Horns

I usually avoid Chevy plugs in Fords. We were taught in mechanics school to put AC Delhi in GM, Motorcraft in Ford, Champion in Chrysler, Bosch in anything European, and NGK in anything Asian. For some reason (probably something in the engineering) they just perform better in these applications.
 

Wildlifer

Old Mossy Horns
Now that I am thinking about it the truck has not had new plugs since the motor was replaced. I replaced them just before the motor went. I would assume they are now motorcrafts. Looks like I will be pulling all the plugs and wires anyway
 

Dan in NC

Eight Pointer
Contributor
Now that I am thinking about it the truck has not had new plugs since the motor was replaced. I replaced them just before the motor went. I would assume they are now motorcrafts. Looks like I will be pulling all the plugs and wires anyway

Good plan.
 

Chad

Four Pointer
I usually avoid Chevy plugs in Fords. We were taught in mechanics school to put AC Delhi in GM, Motorcraft in Ford, Champion in Chrysler, Bosch in anything European, and NGK in anything Asian. For some reason (probably something in the engineering) they just perform better in these applications.

I agree 100% with this. We normally use Autolite platinum plugs in Fords. They are made by the same company as Motorcraft and I have always considered them equal.
 

useyourbow

Eight Pointer
Probably the coil pack for that cylinder. Not certain if that year has the same manifold covers which were aluminum cover in cased in plastic but in my '03 a slight leak started in the manifold cover that allowed coolant into the chamber and fouled the coil pack.
 

Wildlifer

Old Mossy Horns
Probably the coil pack for that cylinder. Not certain if that year has the same manifold covers which were aluminum cover in cased in plastic but in my '03 a slight leak started in the manifold cover that allowed coolant into the chamber and fouled the coil pack.

I don't have individual coils. I have 2 coil packs on the front of the motor and wires to each plug.
 

Hank

Old Mossy Horns
Yes, your correct, that engine is the same engine they put in Lincoln Towncar. They have that crazy 2 coil deal. Each bank has 2 wires stay on that side, and 2 cross over the front of the engine and go to the other sides coil. FWIW, Autolites are the same as Motorcraft. As someone mentioned, use Autolites or Motorcrafts in a Ford.
 

Wildlifer

Old Mossy Horns
Thanks guy. Halfway through and it looks like the plug causing problems may have just worn out faster than the others. A little more ash on it than the rest most likely from a weaker sparks. Gotta head back to the parts store and return the motorcraft wires for autolites. That's what I used last time and it will save me enough to swap out my idler pulley. For the record I had motorcraft platinums in it.
 

witler

Eight Pointer
With 75k on the wires, I would go ahead and do a complete tuneup, wires, plugs, cap and rotor. May also consider fuel filter could be debris inside moving around.
 
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