Ok so I have a 1997 f150 with the 4.6 auto. Last march it started idling rough after towing a pontoon boat. It had been making a strange rattling sound and upon WOT the noise stopped and the truck seemed to tow better. That's when the rough idle started and I've been driving it like that up until now. Well about 2 months ago it started blowing white/gray smoke out of the exhaust but it comes and goes and isn't constant. Now it overheats and cools off completely intermittently. Dealership tells me 0% compression in #4 cylinder. There are no metal shavings in the oil and all other fluids seem fine as well. I would just like to know if maybe I should buy a new motor or if there might be a cracked head or something.

 

Find a good used engine in a junkyard.

 

Yup, glc is right. Find a good used engine. Alternatively look around on eBay for a reman with a warranty.