This was the diagnosis at Ford Motor. The timing chain sounded loose, so I took it to Ford asap. They tell me engine repairs exceed cost of buying a used engine.

Any recommendations? I just put in $1200 on suspension, new tires, and this happened 2 weeks later. It's a 2007 4x4.

Can it be rebuilt, or should I keep an eye on the used motor market? thanks!

 

I don't have a 4 litre, but yours is probably the one where the timing chain is only accessible when the engine is removed.
The new upgraded timing chain kit will solve your problems, if in fact it is the guides and chain.
Any thing can be rebuilt, you save money by doing it yourself and you also have the satisfaction knowing that the job was done correctly.
Used engines are gamble, you never know what you're going to get and how honest people are.

EDIT:
Looks like you already received an answer from Ron, the 2007 doesn't have the timing guide problems.
What was the compression on those three cylinders ?
At any rate, maybe the chain and guides need attention, but as a I said above, anything can be rebuilt _ stay away from used stuff.