2001 F-150 4.6, purchased at 232k, now has 238k miles. Getting misfire code and I have starting replacing plugs and coils and needs some advice based on the condition of the old plugs (pics attached).

6 of the plugs looked reasonably good.

The #4 plug was drenched in oil when it came out, not just a little, like it had been sitting in oil. I am guessing this means this plug was not firing? Is this also a sign of worn/broken rings? Valve Guides?

The # 7 plug was very hard to get out, even after it broke loose, was hard to turn all the way until it came out. You can see why in the pic. I need to know what I need to put back in for that plug. I am not sure if that is an adapter or oversized plug, obviously hole was stripped and this was some kind of repair. Not sure how I match the threads when I put in new plug. Do I look for an oversized plug or do I use a regular plug with some type of adapter?

Any input appreciated.

 

Is that oil, or carbon mixed with coolant? If the latter, it'd be a manifold leak.

If the plug hole is stripped, the cal van 38900 kit works well to fix it. Common problem for our trucks..looks like someone tried a helicoil which isn't very effective because it has nowhere to really seat.

 

On the #4, it is definitely oil. Local mechanic says that is not unusual for a high mileage vehicle, as the truck sits oil runs down into the cylinder.

On #7, the mechanic said it was likely burned because compression was leaking around the plug. I don't completely understand the physics of that and how that burned the bottom end of the plug, but he has been doing this for 50 or so years, so just take his word, LOL.

He said it was an insert and actually gave me another insert and loaned me a tap to clean up the threads just in case.

Feeling a little better about the situation. Now I have just got to research with thread sealant is best and give it a shot.

Thanks for the feedbac\k

 

Listen to what somebody told you here.above
The reason that helicoil came out is because it's a piece of crap.

If you want it to last , and never worry about it again, you're going to have to do it right.

 

ya, that's why the helicoil isnt the best option. Since it already failed once I'd repair it with something else - the cal van, lock n stitch or time cert.

The oil soaked plug - was there oil on the coil plug boot too? I would just say to make sure there isn't a bunch oil in the plug well - there is a little donut seal on the bottom of the valve cover on each plug hole - if it goes that hole will fill up with oil over time then it runs down the plug as you're pulling it

 

There is no Helicoil involved in this in any way, not sure where that came from, it is a threaded insert that came out and same is going back in.

 

​​​​​​There is no Helicoil involved in this in any way, not sure where that came from, it is a threaded insert that came out and is going back in.

No oil in coil plug boot or in the plug well

 

The solid inserts typically are inserted with red (permanent) thread locker (Loctite). Looks like yours wasn't unless the previous guy put it on the spark plug threads instead. You should be able to grab that old insert and unthread it. If you wanted to. Sounds like you don't need to though.

I'll bet it was all burned up because the last guy did the same thing that you did so just put the old plug back in with the insert on it.

 

Update. A little concerned. I ran the lubricated plug thread chaser tap down into the hole, never really felt any resistance as it went down.

Same when I put in the new plug with insert on it, it never got tight and plug wrench felt like it was slipping on the plug. When the threadlock cures, I am going to try to back the plug back out and look at the insert. This insert did not have lip on top and not sure, but afraid it may have gone in too deep.

The original hole may have been too big, but the other insert was tight and there was a lot of resistance when I backed it out. Does Cal Van make an insert with a larger diameter in case I have to drill and tap again?

 

Might be that my post coincided with yours. Take the old insert off of the old plug. Clean it up and reuse it.