OEM Motorcraft Platinum Spark Plugs

[Kamaaina]

Okay all you "rocket scientists", let's see if you can figure this one out: I just got thru re-gapping my OEM Motorcraft spark plugs on my '96 4.0 XLT. How come the plugs on the right side are different from the left side. Left side is AWSF-42P and the right side is AWSF-42PG. The right side plugs have the platinum on the groung electrode (PG) and the left side is on the center electrode (P). I checked the shop manual and it says that this is correct. Am I missing something here? Why would the two banks of cylinders be different from one another? Shop manual says to replace with AWSF-42PP (platinum on center AND ground electrodes). Is this Ford's way of putting in cheap plugs at the factory and ripping you off when they put in the double platinum? What would happen if I switched plugs side for side? Would engine run backwards (wouldn't surprise me)! What was Ford's logic in doing this?

 

[Jason_25]

I beleive it's a money saving tactic.

Why were you re-gapping the motorcrafts? They come pregapped.

 

[Kamaaina]

Just thought I'd check the gaps on the plugs after seven years of driving. They were about .058" average so I reset them back to .052" gap. Only got about 27,000 miles on them and they look like they'll go the "100,000 miles before tune-up". If Ford wanted to save money they could have just stuck in some cheap Champions to get it thru the warranty period. Also would be cheaper for them to stock one plug instead three different platinum plugs. Anything to save a buck.......go figure.

 

[procyon]

Go here:
Dead Link Removed

 

[glfredrick]

I understand that the difference in the platinum is because the coils fire in opposite polarities, + to - on one side and - to + on the other, thus the platinum on opposite sides of the plugs.

If someone knows differently, I will stand corrected.

 

[Kamaaina]

Fire in opposite polarities.....hmmmmm. How could polarities change when all of the plugs are grounded to the cylinder heads? Can't send positive voltage to the ground electrodes because of the negative chassis ground.

 

[Alec]

Yup, they fire oppositely. One side comes with single plat and one with double plat. For convenience, just replace them all with double plat.

 

[glfredrick]

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a double platinum has platinum pads on both the electrode and the ground strap.. Since on distributorless ignition systems, one side of the coil fires normally (from electrode to ground) and on the other side of the coil pack, it fires from ground strap to electrode.. Ford tended to install "special" plugs as OE plugs.. One side of the engine had the platinum on the ground, the other side had it on the electrode.. I don't know if they still do that.
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The above is a quote from another forum (Rough Rangers) on the same subject...

http://host14.ipowerweb.com/~rrorcc...hp3?s=&threadid=11599&highlight=Ignition+coil

 

[Kamaaina]

I guess the "opposite" firing seems to make sense, the coil pack looks divided with three on the left and three on the right. With all of the electronics controlling the engine nowadays it shouldn't surprise me that it operates this way. I guess Ford would save some $$$$$ with these weird plugs as only half the platinum is used versus double platinum. Have to admit, though, on my stock engine the plugs look pretty good after 27k miles with good coloring and no missing.