Plug recommendation requested


#1

I’m working on troubleshooting our F-150 (2004 4.6L) and am planning on replacing the spark plugs. Can someone recommend a quality plug?

I am assuming (hopefully correctly) that the boots and coils don’t really need replacing. My understanding is that if a coil goes out, it goes out pretty quick and is usually due to the misfiring of the plug itself.


#2

I feel the boots should be replaced. Old boots can have carbon tracks and old rubber can crack. This leads to misfires which can take out the coil. I’d stick with the OEM plug and a new sets of boots at the same time.


#3

The same brand and part number plugs that were in the engine when it came from the factory are the ones that you should use. Your Owner’s Manual should list this info.

While–in theory–all spark plugs of the same specification are identical, in practice they often are not, with the result that some engines will run poorly on non-OEM spark plugs. The ones that seem to have the most potential for running very badly are the “advanced” multi-electrode spark plugs, such as Bosch brand. I know of several people whose engines ran terribly after installing Bosch multi-electrode plugs, and once they replaced them with OEM plugs, the engine ran very smoothly.


#4
VDC is on mark..Stay with OEM.The plugs may cost abit more , but its .better to do the job right the first time..Ive seen it happen twice in my mechanc yrs what VCD described ...More recently , my buddy bought bosch plugs based on price, and the Riviera ran worse. I had to do this job twice . When i was done i kicked him !!

#5

I get Motorcraft plugs and wires for my Escort from a big box auto parts store for about the same price as any other OEM equivalent. If it costs more its maybe a few bucks - not worth thinking about.


#6

Thanks everyone.

Follow-up question: the SP-515 is $11-$12 each and the SP-493 is $4-$5 each. What is the difference in functionality between these two?


#7

I generally buy Motocraft plugs for my Ford 302 V8 Ford. And NGK for my Corolla.

I think the best advice though is to use one of the plugs from the list the manufacturer recommends, as provided in the owner’s manual. If the auto parts store doesn’t have any in stock, ask them to order it for you. It is worth the wait to be assured you have the correct plug.


#8

According to Amazon fitment guide, , the SP-515 doesn’t fit your truck. The SP-493 does. Double-check the SP-515 recommendation/fitment. In cases like this, I pull a plug and take it with me to get the right ones. Both are platinum. The SP-515 might be double platinum, but I stopped researching when I was told fitment was wrong.


#9

You refer to troubleshooting and pulling the plugs. Is the CEL illuminated, engine running rough, or what?

If those plugs have been in there a long time, I suggest that you use extreme car removing and installing new ones on the offchance that removal of the plugs could bring some of the spark plug hole threads with it.

The fitment shows your engine uses the same spark plug as the 4.6s in my Lincolns; a ho-hum Autolilte AP-104.
My hazy memory seems to recall that number is a new replacement number which supercedes the old 764 (copper core) or AP764 (platinum) and so on. Three bucks each at AutoZone…
You might verify that number change just to make sure.