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Discussion Starter #1
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?
 

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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
 

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Discussion Starter #4
My pcv valve is still functioning properly so i didn't replace it. my plugs came pre-gapped, i bought them from sacramento mustang.
 

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You may want to pull them and check the gap to make sure it didn't get closed accidentally during shipping.
 

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.052-.054. also check you fuel filter.
 
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