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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6635
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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F150: Mike, I have a 2010 f150 FX4. I have 160,000 miles

Customer Question

Hello Mike, I have a 2010 f150 FX4. I have 160,000 miles on it. I have never changed the spark plugs. getting ready to do that now. Lately I have been having problems at low speed under acceleration. It is like the truck stumbles. I let off and feather and it will clear up.
As time increases is seems to miss a bit at the higher speeds. With RPM up I can climb a hill without a miss. Seems like after I turn and give it gas it will chug or stumble. It is solid enough that my girlfriend says it is the transmission. I know the way the truck runs will effect the transmission. One time I did get a code on #3 misfire, I always get a code for Evaporative emissions P0451. I know replacing the spark plugs will only help. Should I get a coil pak for #3 as well? Does it seem that spark plugs can be so intermittant? The righ runs great the rest of the time. High speed is great. Just seems to go against logic.
Submitted: 2 years ago.
Category: Ford
Expert:  A. Penland replied 2 years ago.
Hello and thanks for using JustAnswer.I will try my best to help you with your question.
The problem you are having is caused by the spark plugs miss firing under a load. Do not replace the coil just yet. Just do the tune up with the spark plugs, I recommend Motorcraft plugs. The Champion spark plugs will cause more issues because they have a different resistance value in them which will cause more miss fires under load.
Then, disconnect the battery for 15 minutes and then drive the vehicle.