So I posted late last week about putting in new plugs and my truck misfiring right out the gate. Come to find out, cylinder 1 and 2 was eating the spark plug. The electrode on the end was bending, checked gap with the old ones and everything checked out. I bought 2 new ones and now cylinder 2 is fine, but 1 is still giving me problems. It has new distributor and plugs when I bought it, wires are all correctly connected to each spark plug as well. It had a slight miss when I bought it but none of the old plugs had bent ends. The guy gave me autolite plugs that were a little shorter than the ones I pulled out so I bought NGK ones that matched the length and everything of the ones I pulled out. All other 5 cylinders are fine except cylinder 1. Should I put a short plug in cylinder one? Should I take an air gun to blow out any carbon build up in the center and try to put a new, same length one? Kinda at a loss with this one. I’m not over tightening either, I thread it in with the plug socket on the plug by hand, until I can’t feel it turn anymore than I do a 1/4-1/2 turn on my ratchet.

 

Best to note Year+Model \ Engin \ Trans \ ... in your Signature+Thread; assuming 2003 Ranger \ V6~4.0L~SOHC Engin \ 5r55e Trans \ 1354 TCase ?
NonOEM SparkPlugs+CoilPack in this engin is commonly a problem: spec Plugs are FordMotorCraft# agsf22fm\sp500 or OrigEquipMaker AutoLite# app103.
Spec Gap is 0i054 = 0m0014, never assume correct, always check+adjust. Use a little AntiSiez on the Threads. Spec Torq is 15pf = 180pi = 20nm.
What Make+Model ignition Wires & CoilPack are you using?
Recommend CoilPack be Removed+Cleaned+Inspected+OhmChecked, reinstall if ok or renew as needed.
Recommend Plugs+Wires along with OxSensors be renewed every 100kMiles\12years.
Click here for more info on this IgnitionSystem.
Click here for more info on these OxSensors.

 

I’m unsure what’s on the truck because when I bought it, the guy replaced that already. I was using NGK at first then switched tried autolite double platinum with .054 gap and still had the same issue

 

What AutoLite plug are you using?
Best to confirm what ignition parts are installed, otherwise you may end up chasing your tail.

 

There is nothing in the cylinder that can hit the end of a spark plug in a 2003 4.0l, picture of 4.0l SOHC head here: https://cdn.shopify.com/s/files/1/04...g?v=1594490515

So there must be a foreign object in the cylinder bouncing around, maybe from old spark plug?

If you have a compression gauge test #1

 

I’m using their double platinum

 

what should I check for on the compression gauge? And what do I do if something happened to be in there? I didn’t see any chunks missing from my old plugs so I’m unsure of what could be in there

 

Compression test will tell you if a valve is bent, exhaust valve could hit spark plug if it was bent, would also have a "ticking" sound from engine
and 0psi compression

You can look inside the cylinder with a bore scope down spark plug hole