My grandfather's '98 F150 runs fine at idle, and light acceleration, but when he punches it, it starts missing and shaking and it acts like it doesn't want to live anymore. I have no idea what it could be, we replaced the plugs a while back with E3 Diamond Fires from O'Reilly. We just replaced the wires with OmniSpark, because my grandma doesn't like to spend a lot. I have seen a lot with these trucks being picky if they don't use Motorcraft brand everything. The truck has about 250k on it.

 

First, get rid of that E3 junk! That crap doesn't even work in Briggs engines... replace with Motorcraft.

Second get rid of those wires. Replace with Motorcraft.

Make sure you thoroughly check and double check (maybe even triple check) the gap on the plugs.

 

Check the fuel pressure. Change the fuel filter if it is low or hasn't been changed in a while. Also, check for codes.

 

 

These trucks respond well to Motorcraft ignition parts, other brands not so much.

 

You get what you pay for - OmniSpark is a cheap wire. At O'Reilly's, Motorcraft wires cost over twice as much. However, you can get Motorcraft wires from rockauto.com for half the price as the same ones at O'Reilly. You can also save on plugs too.

https://www.rockauto.com/en/moreinfo...382756&jsn=453
$64.79

https://www.rockauto.com/en/moreinfo...382756&jsn=476
$3.13 each

 

 

I'd also order some Motorcraft plugs - those E3's won't last.

 

 

Make sure you use a torque wrench on the plugs - 28 ft/lb.

 

Oh, thanks for saving me the hassle of trying to find the proper torque specs. Also, I heard somewhere that Ford changed the recommended oil from 5W30 to 5W20 because it gets to the timing setup faster. Is this true?

 

I think the switch had more to do with the tiny increase in fuel economy.

 

Ah, OK then. I'm glad I found this site, otherwise I would not have known what I now know about the truck.

 

If you look up the torque spec for spark plugs in the factory manual, it will say 12 ft. lbs. which is WRONG. That light torque combined with about 4 or 5 threads that engage has led to spark plugs working loose and blowing out. If you torque them to 28 ft lbs as glc said, they won't blow out.