Alright, I have had my Ranger for a little under a year now, and I decided I would replace the wire-set and plugs sooner rather than later.

And, in short, I was suprised to see the truck was running up until then! All eight of the plugs I pulled were eaten back to about a .08 to .09" gap, where they are set to a .044" gap.

I don't know whether it's the fact there are two plugs per cylinder or what, but these plugs lasted a very, very long time. Longer than they should have lasted. I was hearing misfires whenever I really stepped on it, but other than that no problems except for the truck was burning more fuel. How is that? Was it just because each cylinder has two plugs, or is there something else?

 

Three things happened in the auto world when it came to spark plugs
1. In 1974 they removed the use of lead in gasoline. This in its self extended plug life by a factor of 5.
2.The auto industry started using precious metals like Platium and Iridium in there electrodes. this what made the 100,000 mile plug possible.
3. The use of very high voltage ignition systems
I have seen the old standard spark plugs make 60,000 miles before they started to misfire I have seen them so badly worn that you could not see the electrode above the procleain center.

 

Our Rangers have a paired plug, coil pack, "waste spark" system, in which plugs are paired to fire on their power & exaust stroke.

So they spark twice as often, as the old single coil spark systems & in this paired plug coil pack system, the spark polarity is reversed on half of the plugs.

This means that the spark eminates from the center electrode on half the plugs & from the ground electrode on the other half.

SO, to prevent excessive spark gap erosion over time, we need to use the specified double platinum replacement plugs, of the proper design & heat range, like Motorcraft, or Autolite.

If you used non platinum plugs, like a convetional electrode material, copper core, or single platinum plugs, that may be why you had the excessive spark gap erosion.

If you used single platinum plugs, then half of them were likely excessively worn & the other half not so badly worn, as the platinum would have been on the proper electode, to match the sparks polarity.

Anyway, with that wide a gap, it's sorta like retarding the timing, because the coil has to take a little more time to build enough voltage to bridge the excessive spark gap & worn & rounded of edges on the plugs electrodes require more voltage to spark.

All this adds up to retarded timing & that adds up to less efficient combustion & power output from our engines, so we mash the gas more to make her move & use more fuel in the process, hence MPG drops!!!!!

SO, I hope you replaced your plugs with the specified Motorcraft, or Autolite double platinum type!!!!

 

I remeber back in the 70's you'ld be lucky to get 30,000 miles out of a set of champions (champion was a good ford plug back then). I had 3 pinto's all with the 2.3, I couldn't get 3,000 miles out of a set of plugs, they would get oil bathed and foul. The old 70's 2.3 had weak valve seats, after about 80,000 miles thay would start allow blowby. So "yeah", we've come along way "baby". I haven't had to change a set of plugs in a long time. Since I plan on keeping my current ranger, that could change. After looking at the left bank on the 4.0 sohc, the shop may get that task.

 

Only thing I'd add to the explanation is your wire set was also most likely shot, so I hope also you got a good quality set to go with what hopefully were some double plat plugs. Its money down the drain if you don't do both at the same time. Let us know if your efficiency improves.