I have a '99 F150 5.4 with about 67k on it. Today it started running a bit ragged, and it kept getting worse until you could feel it stumble while idling. No noise was apparent until I opened the hood and there is a very light exhaust leak sound. I'm guessing it's a loose plug on the passenger side but I hadn't read anything about an engine miss being involved. Are these connected or separate issues in your opinion?

Also, how safe (reliable) is the engine after one loosens up if you just replace or retorque the plugs?

Thanks,

 

bump...

sure hope somebody has some ideas or can answer my concern.

Thanks

 

Find the loose plug take it out and see if it carried any threads with it...if not repalce with a new one torgue to spec and forget it

 

Take a mechanic's stethoscope and listen at each fuel injector, each coil, and around each manifold. If the sound is at a coil, pull it and check that plug. If no luck from the above, pull all the plugs and check the plug color, condition, and threads.

 

Thanks for the advice.

It turned out to be two problems, a bad coil on #4 and a warped exhaust manifold. Replaced under extended warranty

I'm still losing confidence in my Lariat. What a shame...