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I have seen the 5.4l engine on the 2007 expedition misfire with no accompanying trouble codes (check engine light). Sometimes it will hesitate and shudder for miles with no code set.
When was the last tune up on the vehicle (spark plugs and boots)?
Your symptoms could also be a restricted fuel filter; when was it last replaced?
A hesitation from the drivetrain? Does it feel like the transmission is slipping?
Does is change based on pushing the gas more or less?
Did the mechanic use Motorcraft plugs? We have a fleet of about 1200 fords, 200 of them are the 5.4l engine. If you use anything other than Motorcraft plugs it will misfire, just as you describe.
Rarely do we get them in with slipping transmissions; they usually just go out completely when they go.
Is it most noticeable when you are just barely on the gas, almost coasting?
Then I would definitely say it's the plugs.
No, they don't misfire right away. They usually start acting up about 5,000-10,000 miles after replacement.
You also have to fill the coil boots with dielectric grease- this sounds unusually, but it is essential to keep them from misfiring down the road.
If they are motorcraft plugs then you may just have to drive it until they set a code. You will also want to inspect the boots for signs of spark jump, which would be caused by no dielectric grease when they were changed.
Aftermarket coils aren't as big of a deal. Most of the brands you can get will perform as well as the factory brand.
Please let me know if you need additional information.
Let me know if you need additional information.
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