2000 Explorer 4.0 SOHC spark plug gap | Ford Explorer - Ford Ranger Forums - Serious Explorations
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2000 Explorer 4.0 SOHC spark plug gap


October 16, 2010
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City, State
St. Pete, FL
Year, Model & Trim Level
2000 XLT
I have a 2000 Explorer XT with Yamaha 4.0L SOHC. Since purchase, I have modified the exhaust-- MaxFlow Muffler with 2 1/2" pipe from the muffler aft. I also added K&N filter for max inflow. Performance in terms of mpg and acceleration were vastly improved. Earlier in its mileage, I would get 18-20 mpg highway and 16 in town (I calculate mpg EVERY fuel stop). The SUV now has 230K miles. Still no oil consumption, still no head gasket issues. About 20K miles back, I put it on a dyno, and the shop suggested new spark plugs. Gas mileage has been down, including most recently in-town mpg is about 11 mpg?!? I changed plugs yesterday. Old plugs were Motorcraft AGSF22N. New plugs are NGK TR55GP (platinum). Gap on old plugs was ~ .050", and they looked OK. But since changing plugs, performance is way up, based on the first 50 miles (only), and accelerating onto freeway. Any thoughts about plug use? How should computer be tuned for air/fuel mixture based on K&N and exhaust mods??? Is MAF sensor OK?