I changed my spark plugs a couple weeks ago at 93K miles. They looked worn. I was expecting to see an improvement in fuel economy with fresh plugs but I have not. I have also lately been smelling gas when I start up and idling at stop lights. Doing some research I learned this is probably from the plugs not being torqued enough. I am going to pull the plugs, make sure that the seat is completely clean and re-torque them. I was just wondering if enough fuel is escaping to account for my lack of fuel economy improvement with new plugs. BTW my plugs are Autolite HT15, found them on clearance at Menards of all places.

 

Yea its probably definitely the spark plugs. To be honest id throw them aside and get some MotorCraft SP-515. Spark plugs are really one thing you dont want to skimp out in these trucks

 

Well I pulled the plugs, cleaned them and the plug holes and reinstalled to proper torque. Now no gas smell. I guess I will track my fuel economy and see what that does.

 

You are completely missing the point. If the plugs are so loose you can smell raw gas, those cylinders are losing compression, which accounts for a drop in performance as well as fuel economy. Plus, you may not realize any increase in fuel economy with new plugs. The old ones were most likely still working fine, but 93K is a good time to replace them.

 

I worded it poorly but that was my point. Before changing plugs I had been having that stumbling issue. Looking it up I saw it could be caused by worn plugs. when I pulled the old plugs they were worn, the truck only had 93k miles on it but in its last life it belonged to the city so it probably spent a considerable time idling, which would account for the wear. The initial plug change solved the stumbling issue but then I began smelling the gasoline. So now I have pulled all the plugs, made sure the threads were clean and re-torqued them and the gas smell is gone. Now to see how the mileage is on the next fill up.