.52 - .56 Only use Motorcraft or Autolite plugs or your car won't run worth a crap after a couple of weeks. Assuming you have the 6 cyl? Duratec engines in the Cougars are notorious for not liking other brands.
The Spark plug location on the 2001 2.5 liter dohc is under the valve cover.
0.054 for 1999 to 2001 V6.
.054
Spark plug order? there is no such thing.
According to one of Fords websites : For a 1969 Mercury Cougar ( all factory available engine sizes ) ( .035 inch spark plug gap )
You can find the correct firing order for your 1987 mercury cougar at www.coolcats.com, it is a website dedicated to the cougar and thunderbird.
According to one of Fords websites : For the 1992 Mercury Cougar , 3.8 liter V6 engine : ( the spark plugs are gapped at .054 inch )
According to one of the Ford websites : For a 1988 Mercury Cougar , 3.8 liter V6 engine : ( the spark plugs are gapped at .054 inch )
0.054 for the 1999-2001, others not sure.
According to one of Fords websites : For the 3.8 liter V6 engine in a 1988 Mercury Cougar : ( the spark plugs are gapped at .054 inch )
.040 ========================================================== According to one of Fords websites : For a 1993 Mercury Cougar : The 3.8 liter V6 engine and the 5.0 , V8 have spark plugs gapped at : ( .054 inch )
Remove the spark plug wire from your 2001 Mercury Grand Marquis. Remove the spark plug with a 5/8 deep well socket, white turning it to the left. Reverse the process to put in the new spark plug.