98 Explorer,4.0SOHC. At what mileage should the plugs and wires be changed?
What is the best way to get at the plugs? What is the best type of wires to buy? There is only 58K miles on the engine,1/3 in town and 2/3 on the hwy.My other vehicle is a 2000 F350 P/S. With the price of fuel,I drive the Explorer.Both get about the same mileage.Diesel is $2.85/gal. v/s $2.25 for unleaded.
Thanks ,for all the replies.

 

In all likelyhood, the owners manual for the Exp will indicate 100K on the plugs. My personal experience on a 4.0 was that at 90K, they were aging but could have done the full 100K. Gas mileage was not suffering at all nor was performance. On the wires, I'm always able to go over 100K with todays heavy insulation wires. The exception might be someone that idles around town thus exposes them to a fair amount of heat. Add to that thought heat from living in a warm part of the country. In your case, it sounds like your plug wires should be of no concern until you hit 125-150K miles. IMO, there is a whole cult of people out there that replace plugs and wires long before they are needed. And this comes from a maintenance fanatic.

*When it comes time to finally replace the plugs, access to the right front plug or plugs might be easier by going through the wheelwell.

 

I'm a maintenance fanatic....have a schedule on Excel...have been doing that since the 80s.
I agree with the magic 100,000 number. I recommend that the whole electrical be done then, that way you'll be trouble free for another 100,000. Doesn't that sound nice?
Plugs, wires, whatever they have now instead of a rotor/cap? Use factory specified Motorcraft plugs and I'm gonna say wires too. There's examples of other brands that cause problems....with these high-tech vehicles.
Since it's only every 100,000 miles, I'm gonna have the dealer do it, or a shop I can trust and I'll specify Motorcraft. Sure it's high, but for 100,000 miles, that's good insurance. You might as well forget about changing your own plugs at 100,000 on a SOHC....virtually impossible. One of Fords' Better Ideas!

 

When you do the plugs, make sure you get the correct numbered plug. I believe your's probably calls for a double platinum plugs. Some places will try and sell you a regular plug, since some of the books call for it. Get the plug type from your hood sticker or owners manual. I also suggest installing the plugs with anti-seize, and di-electric on the plug boots.

 

My initial problem is,an idle that seeks,a sooty exhaust,and a decrease in mileage.
Please,all feedback is deeply appreciated. There are no codes. Advance Auto did a free scan on the Explorer(thank you).
I did a MAF sensor clean. Air cleaner is KN and is clean.

 

Sooty exhaust would be unburned fuel.
How about the Idle Air Control (IAC) motor? Lots of posts on that baby.
Also, clean both sides of the throttle plate.