2004 Thunderbird Engine miss

[4PacificBird]

Engine miss at 50-55 mph under acceleration - excellent at other speeds???

 

[Georgia Cat]

Engine miss at 50-55 mph under acceleration - excellent at other speeds???

Make sure to check the coils.

 

[tlfmd]

Sounds just like when all my coils died at once last spring (2005 Anniversary Edition)

 

[Bubblehog]

Engine miss at 50-55 mph under acceleration - excellent at other speeds???

As others said, the first place to check is the Coil-Over-Plug (COP) units. They are under the black covers on each cylinder bank, and there are eight of them, one per spark plug. See the other information about COPs in this forum. If you need replacements, there are reasonably priced versions on Amazon. However- sometimes the problem isn't a failed COP, but an oil leak from the valve cover gasket that allows oil into the spark plug tunnel, shorting out the plug. You can replace COPs yourself, it's just tricky getting a wrench on the bolts that hold the covers on. I found that a 7 mm metric socket with a ball joint swivel built in made it much easier. When I went to change out my plugs and COPs, on the second plug I found oil in the spark plug tunnel, so at that point I reversed the first plug/coil replacement, buttoned everything up, and went to my trusted mechanic to get the valve cover gaskets replaced, along with plugs and COPs. The valve cover gasket job is considerably more complex than changing pugs and COPs, so I left that to the experts.

 

[Waltbird]

Great information Bubblehog, and spot on!

 

[4PacificBird]

Thank you, Bubblehog! I'll check the COP units.

 

[JW in Dixie]

A clue - "fine until accelerating" - when you accelerate more air enters the cylinders and pressure increases to a point where weak coils can no longer provide enough voltage to jump the gap - thus misfires. A plug that will fire fine on the bench at atmospheric pressure may not do so in a pressurized chamber. My experience. Good luck

 

[4PacificBird]

Makes sense! Thanks