Plugs and correct gap question

[John Zuber]

Ok, decided at at 82K miles I probably should change the plugs/wires in my 2004 ST. There is a sticker under the hood that says Plug Gap 1.32mm to 1.42mm. In looking at the manual it says Plugs AGSF-22PP and again I see reference to plug gap 1.3mm to 1.4mm.



I don't even have a gap tool that goes up that high as a measurement. Nonetheless, .053" is 1.35mm....correct gap? Any advice on correct plugs?

 

[Yardsale]

Those gap specifications are correct. 1.32mm/(25.4mm/in)=0.051968in, 1.42mm/(25.4mm/in)=0.055905in.



I could not find a wire type gauge that wide and used two flat feeler gauges (0.030 + 0.024") back-to-back to set at 0.054"



The AGSF-22PP has been superseded by the AGSF-22FM. I tried to find the 22PP, but could not. The difference is that the 22FM is not a double platinum and dose not have the spec of platinum on the ground electrode. Autolite makes a double platinum, but I shied away, bending to Internet pressure that Autolite plugs are not necessarily made to Ford specifications.



Recommended spark plug replacement interval is 100,000 miles. Unless there is a problem related to ignition, my experience is this is a good recommendation. On a whim, I replaced my last set with about 40,000 miles on them and they looked about new - light tan in color with no center or ground electrode wear and gaped as I set them. There was no need to change them.



I'd pull one or two of the easier to access and check before I put myself through the pain changing them.

 

[swshawaii]

Ditto Yardsale. IIRC, Motorcraft is now using the shorter SP spark plug numbers. Direct replacement for the AGSF22PP Double Platinum is the SP500 FineWire Platinum. Most O'Reilly's stock them for around $5 each. I had the same conflicting gap info linked below and found .054" to be optimal. Remove the passenger tire for ease of access to #3. GL



http://www.mysporttrac.com/shared/msgboard9e.asp?BOARDNAME=MSG&VIEW=1276260



http://www.mysporttrac.com/shared/msgboard9e.asp?BOARDNAME=MSG&VIEW=1284660

 

[John Zuber]

Thanks. I'm installing Autolite double platinum APP 103. I checked two different parts stores and got the same plug number....in fact, it's a step up from the OEM single platinum plug..at least that's what I was told. I'm finding it difficult to get any kind of real accuracy in gap.



Also, I broke the tips off of two plugs (I've only done one side so far) when pulling the wires, and I've seen at least one spot on a wire that's bad.

 

[John Zuber]

Got to thinking and re-looked at the two plugs with broken tips. Those tips are heavily corroded, so they have been broken for quite a while. I've never seen that before. I'll do the other side tomorrow.

 

[Dean Hedin]

Yardsale, I disagree on the 100k interval. 70k max on the original plugs.

Mine were so eroded away (at 75k) that the gaps had opened up by quite a bit.



Once replaced with a decent platinum or iridium plug then you probably can make 100k.



I would recommend changing the wires if you are changing the plugs. And I would recommend the Bosch magnacore silicone plug wires.



My change came about because of a "cylinder misfire" OBD code. It was a bad wire. At that time I went on a holy grail quest for the best wires and the Bosch wires win hands down. They were not that expensive either.



Definitely put the dielectric grease in the boots AND put anti-seize on the plug threads.

 

[Yardsale]

Dean,



My OEM plugs were double platinum and did very well at 100,000; my second set ("single" platinum) also did well at 100,000. So, my experience is as you state for platinum plugs and the Ford, not my, recommended interval of 100,000 miles (for platinum plugs) seems good.

 

[Johnny O]

I change my plugs every 50k, meaning twice now, both times with NGK Iridium plugs. The ones I took out a couple months ago looked good but the gaps had opened up quite a bit. Still have the original wires but I will probably replace them soon.