Just a quick note here. I worked at a dealership-not ford- and the same thing would happen. Turned out 90% of the time switching to an oem oil filter stopped the problem. Worth a try.
Yeah that was my point exactly. I've seen it before and people tend to go overboard with worst case scenarios, and I fixed it by simply replacing the oil filter with a better one that has the anti-drainback valve.
On a side note, I changed my fuel filter a few weeks ago and when I restarted the engine it was knocking- but it was a spark/detonation knock. At that time I had a tank of 87 octane, which I don't normally run. I had also disconnected the battery by accident (the cable was loose and I bumped it). So when I restarted the truck it was not only full of air in the fuel lines, but the computer was relearning the idle fuel trim. I let it idle for a min, and every time I tried to rev the engine it would knock/ping loudly instead of accelerating. After about 2 minutes it cleared up and hasn't done it since.
So my point is that possibly some of the members here with startup knock sounds could be oil filter/oil pressure related, and some could be ignition/detonation related knock. One person says he only has this problem with certain fuel grades- that proves my second point. To help cure this problem I would say to do a carbon removal treatment to remove carbon build up from "inside" the combustion chamber, not the typical cheezy fuel additive treatment that you pour in the gas tank. I'm talkin about using seafoam through the vacuum hose, or boiling water through the vacuum hose.
By using water there's more risk of cracking a head if you don't know what your doing. The water turns into steam and blows the carbon off the top of the piston and the face of the valves etc. Seafoam kind of soaks into the carbon and then burns off the carbon.
