1999 Ford Windstar (Correct Gap) ?

I have a 1999 Ford Windstar LX w/ 3.8 liter engine. I got the replacement spark plugs (Motorcraft AGSF42FM) double platmuims. In the servive manual (Haynes) it says the gap for the 3.8 liter is .054 and .044 for the 3.0 liter. Problem is everywhere else I only see a gap of .044 for the plug in general w/o referencing the engine size. I put 3 plugs in (front) at .054 around 105,000. Ran better for a few months, but now seems to be running a little rough again at times. I figure that this has to do more with not changing the other 3 plughs (firewall side)? Does anyone know for sure the correct gap on these plugs (AGSF42FM) for the '99 3.8 liter ?

Thanks,

AvalonJohn

If you check under the hood you should find a sticker that lists the official gap as .052 - .056. The .054 plugs should be good.

lewisnc100,

Sticker is gone and plug part number has changed. Thanks for the reply.

AvalonJohn

Found something interesting.

The 99 owner's manual page 239 lists the spark plug gap for the 3.8L engine as .042 - .046.

The 2000 owner's manual page 257 lists the spark plug gap for the 3.8L engine as .052 - .056.

This probably explains some of the confusion you're seeing trying to find the right parts since they've got the same engine.

As far as setting the gap. I always gap with the lower number. It want take long for the gap to increase.. The main reason for the spec range is after so many miles you really should pull the plugs check and equal out the gaps to the spec range. In other words lets say you put 15,000 miles on the plugs you pull to check them,if the spec rang is 0.52-0.56 lets say #1 0.53 and #6 has 0.54 and
#5 has 0.53 if the spark plug on number #6 has worn down to that then go ahead and regap to the higher spec..Make all the gaps 0.54. If the gap exceed spec than replace all.. But in most cases no one really ever does this any more. Do to hard to get plugs. Also spec range can be used for cold climate and high alt.and performance tunning.. That was just my 2 cents on gap setting..

Wow, Can't believe there is so much confusion over this. Saturday went to Pep Boys, they said gap was .044, on a Motorcraft parts site it says .044 for '99 3.8. I looked in the garage for the old engine decal and it said the gap was .052 - .056, so that's what I went with for the plugs AGSF42FM for my '99 3.8 liter. Can't believe these gaps aren't more clear.

AvalonJohn

I'm gonna check my sticker tomorrow. I changed my plugs in my 99 with dealer plugs last year and at the time they told me the specified plugs were superceded by a new number. (both Motocraft numbers) I also seem to remember that the gap was a lot wider than I was used to but I think I got it from different sources and they were all close.