What's the deal with different spark plugs spec'd on the right and left sides?

[edwx]

Shame on me! I just bought 6 Autolite XP-103's, a specified plug at NAPA, for my '06 xls 4L. They worked really well in my last xls which was an '03 4L. Lo and behold, when I checked the Haynes manual it says that the plugs on the right and left side are different........you gotta be kidding! So I called NAPA and asked them about it (they're usually pretty good with this stuff) and they knew nothing about it. They even cross-referenced the Motorcraft #'s and came up with nothing. So I called my local Ford dealer and spoke to the parts guy, and even he knew nothing about it. I gave him the two Motorcraft #'s and he came up with nothing either. So unless I find out something drastically different, I'm assuming I'm good-to-go with these plugs.

On an interesting side note, I had a '96 xlt 4.0L years ago, and when I changed the factory plugs they weren't all the same part #.....go figure. So, like I said, shame on me for not checking BEFORE I bought the plugs.

 

[BrooklynBay]

The gap of the plugs should be the same for all of the cylinders.

 

[ZO6_Vette]

I believe my 98 Grand Marquis manual stated that there were two different part number spark plugs due to a limp home mode should the engine loose its coolant.
When I replaced the plugs they were identical.

 

[Willard]

Explorers have always come shipped from the factory with two different plugs in them.

It's rumored to have something to do with the waste spark style ignition system, but I'm not sure.

Replacing them with all the same is fine, makes no difference.

 

[Hitchhikingmike]

the waste spark style ignition system

hu?

 

[Willard]

hu?

I believe the actual waste spark system was used on GM's, but I've heard there is a similar think for our explorer. Basically the spark plug sparks on the ignition and exhaust stroke.

 

[dogfriend]

IIRC, for the 2nd Gen X, the plugs from the factory were a different part number for one bank compared to the other. The explanation that I remember is that on one bank, the plugs only had platinum coating on one side of the electrode (single platinum) while on the other bank the coating was on the opposite side.

Replacement plugs only have one Motorcraft part number and they are double platinum type so they have the coating on both sides.

 

[BrooklynBay]

I think the real waste spark system might be on the older 2.3L 4 cylinder engines with 8 spark plugs.

 

[edwx]

Yes, the gaps are all the same, I understand that, but in the Haynes Manual starting in 2005 they give a Motorcraft Part # for the right side plugs and a different Motorcraft # for the left side plugs. The manual is out in my truck right now or I would list the #'s. I'm not too worried about it, it just seems weird.

 

[stein78]

Any Ford engine that has Coil Packs and spark plug wires is a waste spark setup (typically pre '99 models - at least in the Modular engines). It always fires two spark plugs at the same time. The Coil Over Plug ignition systems are not waste spark. They also do not have spark plug wires.

 

[edwx]

Then how come Haynes only started spec'ing different plugs for each side in 2005? This '06 4.0L looks the same as my '03 4.0L. And how come the Ford dealer (or NAPA for that matter) didn't know anything about it? And yep.....I pulled the factory plugs yesterday, and sure enough, the left side (pass. side) are AGSF 24PGM, and the right side are AGSF 24PM. I'm sure the Waste Spark Setup is a valid explanation, even though I'm not sure what it is, but it doesn't explain everything. I just replaced all the plugs with Autolite XP-103's. I'll have to do some more research on these two AG... Motorcraft plugs. Thanks.

 

[bisjoe]

I'd go by the Ford parts department over Haynes.

 

[aspitaletto]

i was reading this just yesterday in the Haynes manual, i have never heard of different plugs for different sides of motors....

just seemed weird, but that one poster was saying about the coating being on just 1/2 the plug is understandable with the mentality of ford's cost cutting