Spark plug gap on 5.0

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Mar 17, 2014 | 05:14 PM

bigdaddyII

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Spark plug gap on 5.0

A few weeks ago I read a thread here about someone having his truck In to the dealer for a rough idle, and the ensuing issues with plug gap and who was responsible to cover replacement. My truck has a similar rough idle and I decided to investigate.

I asked here about what my plug gap was supposed to be as I didn't have access to my owners manual at the time. The specs I was given (.041-.047) is what I followed and recapped my plugs .045. The idle improved a great deal.

Now I was wondering and finally got around to checking my owners manual after I read somewhere that the gap for the 5.0 changed between 12 and 13 model years. What I found in my owners manual is that the gap I'm supposed to have is from .049-.053. My plugs were out anyway at .057. I will leave them be at .045 but am wondering why the change from .041-.047 on the 2011 model years to .049-.053 on the 2012+ model years? I assume the engine hasn't changed, so am curious of the thought process. TIA for any ideas.

Mar 17, 2014 | 06:15 PM

svt2205

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I honestly think the .041 - .047 range listed in the owners guide is incorrect as my 2011 service manual shows .049 - .053

The plus I pulled at roughly 93K or so were in the .052 range and the one's I replaced them with were gapped at .051. And there was no change in idle smoothness or at any other engine speed.

Mar 17, 2014 | 06:22 PM

bigdaddyII

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I had 38.xxx on my plugs and they were all at .057. Weird.

Mar 17, 2014 | 06:36 PM

PrinceValium

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From: Northern California

Who knows if the gap was set right to begin with...but I am sure you know that as your plug wears your gap gets bigger from the electrode wearing down. (at least on most plugs)

Mar 17, 2014 | 06:48 PM

bigdaddyII

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I understand about the electrode wearing. But from .053 to .057 in 38,xxx miles? While I don't believe that they were gapped correctly to begin with. Why the sudden change from 2011 to 2012? I know of at least a few 2011 who specify the .041-.047 gaps so I know it was listed as such for a least a while in 2011. What's odd is that my truck seems to run better with the smaller, incorrect gap.

Mar 18, 2014 | 08:13 PM

bigdaddyII

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I replaced the plugs today with Bosch Iridiums. I know Bosch is typically a no no for spark plugs but that was all I could find. They were all gapped at .044, so I set them at .049 and slapped them in. Again I marvel at how easy it is to access the plugs on this engine with removal of anything, so if the Boschs give me any issue it won't be such a big deal to swap them back out. I was a bit nervous with the Motorcraft plugs after regapping and bending the electrode around on plugs that have already been through many heat cycles. Time will tell I guess.

Mar 23, 2014 | 11:47 AM

PrinceValium

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I remember the days of the split fire plugs and how they advertised it gave better fuel burn etc.

I don't know if the Bosch will be in the right heat range for your truck...but hope they work for you.