My nephew recently acquired a 1999 Ford F-150, 4.2 L V6. The little guy looks great. White single cab, cruise control A/C and 364,000 miles on it. It has been reeking of gas when running. Recently we changed the brake pads, serpentine belt, plugs, wires and Coil pack. The engine on start up runs like a washing machine out of balance. IT shakes. The whole truck shakes. It feels like it is missing. The #2 spark plug is fouled out bad almost like there is no spark, but there is. The truck is running way too rich and just smells strong of gasoline. What could this be? I've never seen anything like this with this pup of a truck. IT looks nice and rides nice but I am really worried and have had him not drive the truck until we can pinpoint the problem.

 

That's a lot of miles.
Check the compression. If it's low, it needs a rebuild.

What codes are being thrown. That is the first thing to post when you have a problem.

Misfiring as bad as you say will cause a lot of unburned fuel to go out the exhaust. That is probably why you smell gas. The cats may need replacement. If they don't need replacement, they will need replacement soon with the enigne missing like that.

 

I would suspect worn and leaking fuel injectors.

 

I just bought a '97 F150 4.2 in March with 105k miles on it. Seemed to run fine, but after I bought it I realized it ran really rough and would code.

The first things I found out were: EGR needs to be cleaned. Originl upper intake gasket fails often. If you have the plastic upper intake - look into new isolator bolts. Underneath the throttle body is a rubber 90 degree vacuum elbow from the PCV. Check it for a hole. Behind the upper intake, coming from the PCV I had another leak.

I'm currently working on figuring out my IMRC problem.

BTW - maybe if it shakes really bad you should look into the mounts.