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Tune up-better milage????

919 Views 5 Replies 4 Participants Last post by  mf150
I recently swapped out my stock spark plugs at 91,000 miles on my 98 gt with ngk iridium plugs. $8 each. and put on a set of ford 9mm racing wires, i was hopping to get rid of the pingy noise when accelerating and improve my gas milage. i was getting about 19 mpg before and now im getting 17 mpg. What do i need to do to fix this?
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did you change the air filter and PCV valce also?
If your mileage dropped perhaps your running your plugs with the wrong gap size?

But 19mpg wasn't too bad. Right now I'm trying to figure out why I'm getting 13mpg.. :happyhapp
My pcv valve is still functioning properly so i didn't replace it. my plugs came pre-gapped, i bought them from sacramento mustang.
You may want to pull them and check the gap to make sure it didn't get closed accidentally during shipping.
.052-.054. also check you fuel filter.
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