This is what the original plug from 1998 looks like

[PAExplorerXLT]

I had a little shaking that my mechanic thought new plugs and wires should fix. It turned out that the plugs were OEM Motorcraft. After 164,000 miles, this is what one of them looks like. Just look at the gap.

 

[drdoom]

Not too bad! Motorcraft quality! I changed mine at 100K when I bought the truck.

 

[AP9]

Looks better than the spark plug in my lawn mower after one season (~25 hours) of use. Comparing apples to oranges maybe, but still.

 

[PAExplorerXLT]

They replaced them with NGKs. The other thing he pointed out was a whitish discolorations on plug wires. He said they are caused by arcing between wires. Is that right?

 

[swshawaii]

Agree. My gaps measured .065-.085 at 46k. Note center electrode wear on drivers bank due to the "waste spark" ignition.
Did the new plugs improve your lean condition? After all your troubleshooting, may be time for LOWER intake gaskets, yes?

 

[PAExplorerXLT]

I will find out tomorrow morning if this did anything for the cold idle issue. The main reason I took it in was for coolant leak. It turned out to be that black plastic housing that everybody here suspected. He said he had to get the part from Ford for some reason.

 

[bluestream1]

Your MPG must have been horrible..

 

[D.R.Ball]

Tune up's ,save gas and money...I guess I have to put up on my 1995 Ford Explorer as to when the last owner changed the plugs.......Can anyone guess......I do not know but she run's fine(NOW WHERE IS THAT SOLID WOOD BLOCK I USED TO KNOCK ON)?I know a new set of plug, plug wires and a new coil pack that's the gift that keep's on giving.....As well as a change of oil and change of ALL fluid's????(The hell you say, but your cheaper than alimony ).Or getting a taxi.

 

[PAExplorerXLT]

UPDATE

New plugs and wires are definitely noticeable. I had a bad case of vibration standing still with foot on the brake. That is mostly gone. Also, either I am imagining it or my cold idle issue has improved remarkably. Can they be related? Considering that the mechanic swears there are no vacuum leaks left to plug may be the new plugs helped. But get this. I reset the lean code and it hasn’t come back yet. If it stays off then something definitely changed. I don’t see how new plugs can fix a lean condition though.

 

[D.R.Ball]

The computer is using the 02 sensor so it can tell if the engine is running lean or rich, that's what they are for after all....If the computer is sensing an low spark output by the spark plugs it will cause the computer to change the mixture to keep every thing with in limits....Even if it means leaning out the mixture....Everything on these engines is feedback looped and computer controlled...

 

[AppleWood]

Ha! I just changed plugs, wires, and coil pack (141,000 miles) as well while chasing P0171/0174. One of the plugs gapped at 0.102" - just a little out of spec, eh? Also had one wire arcing and leaving noticeable trace on valve cover.

Quite honestly truck ran okay but surged a little on cold start. And CEL came back on, so I'm still chasing vacuum leaks.

 

[Tbruz]

Applewood
Check the 90 degree elbow on the PVC line for cracks or collapse.
With those codes there's a good chance your vac leak is there.
Tbruz

 

[swshawaii]

P0171 & P0174 4.0L SOHC's 2001-03 Sport and 2001-05 Sport Trac
http://www.explorerforum.com/forums/showthread.php?t=314670

 

[BrooklynBay]