I just changed the plugs for the first time on my 1994 Ranger. It has a 4.0 and 55,000 miles. I am the origonal owner and I know the plugs have never been out before. They were easy to remove and unscrewed cleanly. The toughest part was pulling the wires off the plugs.
What was odd was on the passanger side the plugs were Motorcraft AWSF42PG - a standard looking plug. On the driver side the plugs were AWSF42P - a platnum looking plug. Why would the factory put 2 different plugs on the same engine? Wierd
Just thought I would share.
-greg

 

What type plugs did you install? My 2000 Ranger had two different types of original plugs, one type on one side and a different on the other side. I replaced mine with double platinum plugs on both sides. This has to do with the "waste spark" system that the 2000 has. I'm not sure if the 1994 is the same but if you had two different type plugs like mine you may have the same system. I'm sure someone else will chime in with more in-site. If you do have this system you either have to put the same type in each side or get double platinum plugs like I did. If you don't one side of the engine with "eat" the plugs rather quickly and you'll end up replacing them again real soon.

 

I hope you replaced the pugs with double platinum!!!!

The reason is, because of our "waste spark" ignition system.

On one bank of cylinders, the spark eminates from the plugs center electrode, & from the ground electrode on the other bank, because the spark polarity is reversed.

Also on the waste spark system, all plugs are connected in pairs, such that they are also fired on the exhaust stroke, when the companion plug is being fired on it's power stroke, so on this system, plugs work twice as hard.

The factory plugs, to save some production money, have platinum on the center electrode on one bank, the ground electrode, on the other bank, so it matters for electrode erosion reasons, which bank the factory plugs go back in.

We should use double platinum replacement plugs, that way, it won't matter which plug goes where & the double platinum Motorcraft or Autolite plugs are designed to tolerate the extra work load & heat.

There is a multipage "Why use double platinum plugs" thread, in the "Tech Info" thread, located atop this forums thread listing page, thats good reading.

 

I tried to open the Tech Info thread once before but it didn't work. I just checked it again, lots of great info.
I used the Autolite DP so I guess I am good to go. Thanks.
-greg

 

Your good to go. Where is this "Tech Info"? I just can't seem to find it.

 

Azu, scroll up to the header on this page & click on "Ranger & B-Series", when that page opens, click on the first red "Read First", Tech Info thread. Lots of good info there.

 

Wow! That was right before my eyes the whole time! Thanks!

 

See also: http://www.miracerros.com/mustang/sparkplugs.htm