Ford F150 - Engine knocking at startup

I've had a slight knocking when I first start up my truck that eventually seems to go away once it's at normal operating temperature. I was hoping changing the PCV valve might help but unfortunately it's still knocking when I first start it up. What do you guys suggest I try to get rid of the knocking? I use 5W30 oil which is recommended. That's what I've always used. Should I try going a little heavier starting weight like 10w30 since the problem only seems to be when the engine is cold? Should I try sea foam and see if that helps? Maybe I have some carbon buildup in there, I don't know. I just changed my oil about a month ago so I guess I'd have to wait a while before going the sea foam route. Anyway, any suggestions would be appreciated. Thanks.

nothing you can pour into the engine is going to fix the problem. Just take it to a shop and have them diagnose it. A startup knock can mean a lot of things.

Seafoam wont help you with the knock, I found a product at O'Reilly Autoparts and boy I'll tell ya what, the stuff that I found was golden like honey but thicker than molasses on a hot january day, put it in my '99 Century and the knock went away, Im not sayin that it will cure your knock but ive put on 30k miles on the 3.1LV6 in the car and it hasnt knocked since.

Ask your local O'Reilly guy for "anti-knock" additive, that might curb the knock for now, however I do have a question to ask you, first, what engine do you have? secondly, does it sound like the cam grinds or is it more of a rod knock?...let me know how things work out!

I had a similar problem on a 4.0L 2001 Explorer Sport, and found out that MotorCraft oil filters have a one way valve that prevents drainback and keeps the oil system primed. I was buying other vendors' less expensive oil filters, went back to MotorCraft, and the problem went away. I can't say it's a cure for what you have, but for a few bucks for a filter, it's worth a try.