The truck is a 2001 4.6 F150 Automatic with 135K miles.

The truck had a plug blow out on #2, my buddy owns a shop so he helicoiled it for me. Worked ok for a day or so but started missing again but with no codes. I drove it for maybe 500 miles until it threw a code for missing on #2 again. I pulled the injectors to get them rebuilt to see if they may be clogged.

We pulled the #2 plug while the injectors were out being rebuilt and it was melted down into the threads and the helicoil came out with it. We put in a new plug, helicoil and rebuilt injectors and it was still missing so we checked the signal to the COP and injectors and both were fine. So now we know we have spark and fuel...

Now we compression check the #2 and we have pretty much zero compression...so we blow air into the cylinder and it's leaking into BOTH the intake manifold and exhaust... we turn the motor over several times and same thing each time...

So...burned valves? Stuck valves?

How much of a PITA is it to replace the valves on this engine? The worst part is Im selling it so I have to get chin deep in her for someone else

Any ideas? Any good tutorials? Search of google and forum came up dry.

 

The plug with helicoil

 

Use timesert. Heli coil is crap and doesnt work for ****. Not sure about the compression issue though.

 

Sounds like some metal has lodges on the valve seats from the repair job.
If there was no issue before the plug blew chances are it's not burnt valves.
The intake on these motors runs cool so it's not a burn issue IMO.
Good luck.

 

the helicoil repair job might have had something to do with it....try a time sert next time....

 

People will learn one of these days. No matter how cheap $ a heli-coil is, it's not cheaper in the long run.

If you're sure you've got air coming out both valves, then you have something holding them open. No telling what; the heli-coil at least looks intact in that photo, and you should be thankful you got it out. Now, leave it out while it's out. I'm currently helping a customer who had a heli-coil continue threading in until it threaded completely out the otherside of the spark plug hole. Yes, it fell down into the cylinder.

Where's the electrode off the end of the plug?

 

The shop went with the helicoil, had I known then what I know now...it would have been a time-sert. At this point though the only way I can think to fix it is to pull the head, agree? I don't want to but I see know other way.

I checked it three times and air is definitely coming out both valves...
The Ground Electrode was cooked off in the cylinder! The center electrode is still there. It's like a CSI case, what could have caused it to get that hot? The spark arcing to the spark plug instead of the ground electrode? A valve stuck open?

 

if you see that tail that's in the image, that is what will cause the most damage to the cylinder and or valves.....typically with a bolt it will bend out of the way or break off but with a spark plug the ground will get hooked on it and cause the spark to go nuts....

 

That plug doesn't look burned - there's something banging around in the cylinder that caused that damage. whatever that was probably damaged the valves (both of them). You're looking at removing the head, and replacing the valves and valve seats on #2. Hopefully the cylinder walls aren't too badly scored.

Since you're selling it, you might just get a junkyard head to replace it and hope for the best.

 

So where is that tab supposed to go? From the looks of it it does appear that the arc was hitting the tab instead of the electrode causing it to burn. Originally I thought it was just banged up too but at closer examination it's burned past the thread of the helicoil, if it were just banged up that area would have been protected.

Any good write-ups on removing the heads and replacing the valves?

 

Do you think a junkyard head would be cheaper than replacing the valves?

 

that center J shape is suppose to be broken off before anything else is threaded into it "reconditioned threads"....look for the slight indentation, that is a pre-stressed break off point. and it helps lock it into place. agreed, prolly whats under a valve

obviously it isn't really meant for this application

 

Yep....they were never really meant to be used for spark plugs....in my opinion