I'm at 135k and my truck seems to be running fine. The previous owner only had the truck for about 8 months before he sold it to me. He said that he wasn't sure if they had been changed and wasn't even aware that they were such a big issue. The only thing weird I've noticed about my truck is the bucking power in overdrive. I can be going 60 and when I increase my speed the RPMS just jump from 1200 to 2200. There is never a smooth RPM increase in that speed range. What are some other signs of a needed sparkplug change?

 

IMO, the gaps become out of spec at around 60k miles. I know people say they don't change them until 100k+, but how long were they driving with huge gaps? I changed mine at 75k and they were way out of spec. I think you will notice the improved performance instantly, unless they were changed before you bought it. I would change them just to know what is going on, or pull one and look at it, at least.

 

Yeah even though it's seems to be fine, maybe after you change them you'll notice a difference.

 

My 2004 will get new plugs in 2 weeks. My reasoning is with lower carbon build up in only 41k miles the chance of a plug breaking is reduced. When I took my truck to the dealer for the airbag recall, they gave me a price of $600 including plugs no matter if none of the plugs break or all of them break.

In 2 weeks, we'll see if I am right or not.

 

Dealer did mine at 33,000 miles 2 were a little sticky and the rest came out easy

 

Is there a way to tell if they were changed? It would be running pretty rough at 135k if they haven't been changed right?

 

i'd take a look at them about every 75k but uneaded gas burns so clean that your plugs last a freaking lifetime now. i would however check them out, measure your gap and so forth.

 

I changed mine at 117,000 and they were pretty bad. I had a low grade misfire around 1200-1500 RPMs. I thought it was OD going out of the tranny. Changed the plugs and it got rid of that, idles smoother, shifts smoother and has better power. Here's a pic of the worst plug, however the others weren't too far behind.

 

Here's my worst at 118k, not too bad, huh:

 

Notice the gap in the picture MTM Ford posted. It looks like a good 1/4" or .25." The spec is something like .054" IIRC. Huge difference. My plugs looked like his, with hardly any electrode showing.