So I've had my Ford F-150 for a few years now. It's a 2001 and up until the other day it was running and sounding like new. On the way back from work I stopped at the gas station to fill up. When I started it up again and ever since then, it has a ticking or clicking sound only when you step on the accelerator. When it idles you'd never know there was a problem. I've checked the oil and all Tranny and everything is fine. It's a V8 5.6 litre engine. It's got 280,000km or so. Is it an easy fix or do I have to do a rebuild?
Your issue is most likely that your engine is pinging or knocking due to either carbon buildup or poor gas.
My suggestion is if this is a gas station you've never used before, it may have been the gas which is at fault. When the gas gets down a ways (half tank), try putting some high octane fuel in instead of whatever you used (like 91 or 93 if available) and see if the noise goes away. If it does, it probably needs an intake tract cleaning. It could possibly also use a tune up if it hasn't had one recently.
My favorite method of intake tract cleaning is to do a Seafoam treatment. It can do wonders for how your engine runs and should take care of the ticking noise you are hearing.
You may have incidentally developed a minor exhaust leak at the exhaust manifold. That can sound exactly the way you describe. The fix, if this is correct, is to replace the exhaust manifold gasket or possibly the exhaust "doughnut" where the exhaust manifold connects to the exhaust pipe.
Suspect the manifold gasket if the ticking is low frequency, the doughnut if the ticking is high frequency.
its difficult to say where a click can be coming from, another there are several ways to attempt to isolate what general area the clicking is coming from. If the click is rotational meaning there is a frequency and period associated with it, and that on more load the clicking gets louder, look to find the source where-ever a rotational element is (wheels//cam//crank) I had a click to my car and it was a crank bearing that was offset due to oil starvation, so when the car was on load it would get faster, that motor blew eventually. Another thing can be the injectors on the vehicle, have you attempted to use a ford forum? you may get a better response there.