spark plug concerns...just changed plugs, used NGK TR55...trunk runs like crap, my concerns are the original plugs are the half thread type with all new plugs i am able to find having a longer threaded portion which, in my mind is allowing the plug to be threaded deeper into the head, closer to the piston

every recommendation for plugs suggest ones that are the same "long thread type", the original Motorcraft AWSF 32PF, a half thread plug has been replaced with the long threaded plug...don't, the new plugs go deeper in the head that the original

what are the correct plugs that are currently available for my 1997 F-150 4.6

 

The correct plugs are the fully threaded Motorcraft SP432. They are a direct replacement for the half threaded plugs, they do not go in any farther, distance between the seat and tip is identical. Torque them to 28 ft/lb to help prevent loosening and blowout.

 

thanks...now i have to figure out why it's running much worse than before i changed the plugs

 

Your engine doesn't really like anything except Motorcraft plugs. The TR55's are copper, not platinum. What are you running for wires and coil packs? Did you use a SMALL amount of dielectric grease when you changed the plugs?

 

off the shelf wires from O'reilly...coil packs are original. this started with a slight miss/skip/stumble accelerating and cruising around 60 - 70 mph, the check engine light came on...the code reader said it was a bad plug, which prompted me to change them...i read quite a bit before buying plugs and a lot of people stated they run the TR55 plugs in their 4.6 ford without issues...i've always used NKG plugs in all my other cars with good luck...as hard as it is to change the plugs in these trucks i'm not excited about changing plugs unless i can rule out that the new plugs are the problem, which goes to my original question about the thread length and depth into the head

there's no indication the coil packs are bad and i don't follow replacing parts hoping to find an answer without knowing there is a fault with the part i'm replacing...the truck only has 101,000 miles and the plugs i just replaced were the original plugs and most still looked good...

 

I know you don't want to shotgun parts at it, but I'd suspect those aftermarket wires. Motorcraft wires aren't that expensive at rockauto.com. Not saying that the wires ARE bad, but just saying. Did you clean the coil packs and use dielectric grease when you changed the plugs and wires? I know on my V6 I've gone through 2 coil packs, they do develop cracks.

You may want to use a good scanner to check live data, I'm betting it will show a definite ignition problem.

EDIT: Motorcraft wires at Rock Auto are 60 bucks, looks like the O'Reilly wires are just as expensive. Motorcrafts at O'Reilly are over 100 bucks.

 

we did clean the coils and used the correct grease when installing the plugs & wires

 

ummm there’s a code for bad spark plug?
yet you changed spark plug wires with some elcheapo crap, even though you had a bad spark plug?

sigh...

 

which is best....Ford or Chevy...the age old argument that never ends or has a definitive answer....depending on who you are talking to...or is it you always get what you pay for?...your cheap wire comment perplexes me...i came here looking for help not off the wall remarks

FWIW...i ordered a set of MotoCraft wires and a pair of new coils from Pelican that arrived today...maybe with those parts i can get a better response...if my issue persists

 

welcome to 1997, when modular motors do better with motorcraft ignition parts

oh wait

 

although i bought new wires as earlier recommended, i still disagree with ....oh wait

 

Anything but Ford/Motorcraft ignition parts on these trucks is a step down.