differing spark plug gap info on 99 Ford Taurus


Old 01-20-07, 10:46 AM
ddr is offline
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Join Date: May 2006
Location: New York City
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differing spark plug gap info on 99 Ford Taurus


Iíve got a 1999 Ford Taurus SE with a V6, 3.0, OHV (12 valve) engine. I went to change my spark plugs and am having some trouble with the gap size. Sorry about the long post, but I want to paint as clear a picture as possible:

The old plugs are Motorcraft Platinum plugs; I went with some Champion plugs from an auto parts place. The ownerís manual, the sticker under the hood, and a Haynes manual all say to gap the plugs from .042 to .046, so I split the difference and gapped them all at .044. After installing the new plugs, the car was running far worse than it was before. I decided to check the gap on the old plugs to see if they were gaped closer to .042 or .046 and was surprised to find they were gapped at about .056 (these plugs were installed by Ford). Thinking it might have something to do with the platinum plugs, I bit the bullet and went to Ford to pick up the insanely expensive Motorcraft Platinum plugs.

While there I asked the counter guy what the proper gap should be, explaining the the difference between the old plugs and the listed gap size. He said that the plugs come pre-gapped, but I should check it against what the manual says. Just then a guy wearing a mechanics uniform came in. The counter guy asked the mechanic what the gap should be and he said he thought it was about .056, but when I told him about the listed gap size he said I should definitely go with that. The counter guy tried to find a manual with the specs but couldnít locate one. Nice.

Once home I checked the gap on the supposedly pre-gapped plugs and sure enough they were .056. So, did the person who put the old plugs in not bother to gap them thinking they were pre-gapped, or is this the correct gap and the hood sticker and manuals are wrong? Iíd rather not go the trial and error route and keep pulling the plugs and re-gapping them until itís running right (I KNOW Iím going to snap the plug tail or cross-thread the plug hole).

By the way, the wires between the plugs and the coil pack are brand new Motorcraft wires and Iíve triple checked the firing sequence and the connections, so unless thereís a defective wire in the bunch, they arenít the problem.

Thanks in advance for any help.
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Old 01-20-07, 10:55 AM
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What ever the car says and manual, use that gap. Fords are VERY particular about the brand of plug to use. If the manual says use Motorcraft XXX then use them. This happened to me in my old Ranger. I replaced the plugs with what the autostore said to, and it ran like crap. Once I replaced the plugs with new OEM plugs, it ran perfect.
Old 01-20-07, 03:06 PM
Join Date: Jan 2007
Posts: 81
differing spark plug gap info on 99 Ford Taurus

Your first mistake was buying Champion plugs. The last time I did that years ago on a 71 AMC Hornet SC360. The car ran good for about 1000 miles and then, well do I need to say more. The same goes for the company ford work truck that I replace the plugs with Auto-lite Platinums, they didn't last long ether. Had trouble with Champions in my boat engine. The boat engine loves NGKs and lasts 3X longer and went to NGKs on the Hornet with the same results. If I buy auto parts store plugs it is one of the 2, NGK or Bosh.
Old 01-20-07, 03:57 PM
Join Date: Dec 2001
Posts: 2,538
not going to tell you what brand of plug to use as most any brand plug will work fine if they are installed properly even champions although if they got dropped by you or at the parts store dont be surprised if you get a defective one every once in awhile.
would suggest you use the gap on the sticker under the hood but it really doesnt matter if its .042 or .056 as the car should run fine on either one with no misfire or running rough condition, the gap has to be way off to cause a misfire if its still running rough after installing the new plugs would suggest looking elsewhere for the problem.
if the old plugs had any mileage on them at all you should expect the gap would be larger than spec as normal wear will increase the spark plug gap.
Old 11-25-12, 12:00 PM
Join Date: Nov 2012
Location: USA
Posts: 1
1999 6cyl, 3L, DOHV spark plug gap

I have a 99 Taurus too. The original plugs had a gap greater than .055. Ford web site said
.042 or .046. I checked Autozone and Pep Boys. Both said .054. I set it at .054 and it runs great!
Old 11-26-12, 11:01 AM
Join Date: Oct 2000
Location: Livonia, Michigan
Posts: 923
... this proves what bejay said, that the gap has to be way off to make the engine run badly. Regap to .044", and it'll run great as well! Stick with the gap specified on the underhood sticker. I think the Ford web site trumps Autozone, Pepboys, and whatever a Ford mechanic cites from memory.

The previous mechanic probably didn't bother double-checking the gap, and installed them right out of the box. Some spark plugs with the same number have dual applications, and may have been gapped for the other application.

So gap them at 0.44" (as with my 01 Sable, 3.0L Vulcan vin U), and you'll be fine.

ddr, are you having drivability problems? You seem to suggest it at the end of your post.
Old 12-05-12, 06:54 PM
Join Date: Nov 2012
Location: USA
Posts: 7
I've been a tech in a Ford Dealership for thirty years and one thing I've learned is that Champion plugs do not function correctly in a Ford. The ignition system can easily jump any gap you set the plug to so I really wouldn't worry too much about that. If it were me, I would set it to 52 and use Motorcraft plugs.

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