Spark plug #2 keeps getting fouled up

[Mounty99]

1999 Mountaineer 5.0
Original engine and tranny
317,000 miles

Hello all. My beloved Mountaineer is nearing the end. About every 2500 miles, my #2 plug keeps getting fouled up to the point it starts missing badly. Anything I can do other than keep changing the plug every three months? Any suggestions appreciated...

 

[410Fortune]

Injector is failing?

Do a compression test you maybe lost a valve seat in that cylinder and no amount of fixing will restore compression
If you lost a valve seat (common with those miles, it actually disintegrates and gets chewed up and spit out the exhaust) the. Your compression will be down around 60-90psi and that would explain the issue

Otherwise your injector maybe getting lazy
At that point I would replace all 6 and keep rolling!

 

[freak]

My 4.0 OHV was doing that on #1 and I checked everything with no real cause found. I don't like to throw parts at it without troubleshooting. I checked the wires and they all measure good with a meter. Didn't want to replace them. Got so tired of it I said the hell with it and bought a new set of wires. It ran like a dream after that. No more fouling and spark knock. YMMV.

 

[Mounty99]

Thanks all. Put new plugs and wires on about 12 months ago. Ran little better, but same problem with #2.

Got a compression test also and it wasn't too bad considering engine in 26 years old:
#1 - 120
#2 - 100 (oil on plug)
#3 - 100
#4 - 120
#5 - 100
#6 - 110
#7 - 100
#8 - 100

Any thoughts considering the info above? Thanks!

 

[410Fortune]

Add capful of oil to cyl 2 see if compression comes up
Those numbers a little Low but within 15-20% of each other so it’ll run
Could try a different coil pack, you can actually swap the two coil
Packs and see if the fouling moves with the coil

These trucks only have 4 coils they are “waste spark ignition” so two cyl fire off at the same time
You maybe have an intermittent coil? Just grasping at straws

Other things to try is reseal the intake with new gaskets and consider new injectors and o rings at same time. Could pop
Valve covers off and have a look at the rocker arms

 

[harleybidness]

1999 Mountaineer 5.0
Original engine and tranny
317,000 miles

Hello all. My beloved Mountaineer is nearing the end. About every 2500 miles, my #2 plug keeps getting fouled up to the point it starts missing badly. Anything I can do other than keep changing the plug every three months? Any suggestions appreciated...

Change the spark plug to Motorcraft AWSF-42P or direct replacement.

 

[harleybidness]

Change the spark plug to Motorcraft AWSF-42P or direct replacement.