I'm having problems with my 97 f150 4.6 knocking after being started up. If it's cold it will start knocking immediately when cranked and will do so while idling or under acceleration for a few minutes until it warms up. The knocking sounds as if the engine is low on oil but it's not. Any ideas of what this could be??? Thanks

 

This could be bad news for your engine. Does it sound like a deep internal knock? Does the motor lose oil between changes? An engine flush may clear any clogged journals, but that may magnify the problem also.

 

Sounds like piston slap. Pistons are a little loose in the cylinders when the engine is cold, noise will go away when warm because the pistons expand.
Don't know for sure if 4.6 had this issue but 5.4's of that era did.

 

It doesn't sound like it's too deep in the engine, just below the valve cover maybe??? If it's the pistons slappin is this something that I should be worried about and is it a pretty big fix?? Thanks for the feedback, anything helps. I'm a Jeep guy and just got this truck from my dad so I'm not too familiar with it yet. I like to work on it myself if I can. He bought it brand new in 97 and has never had any magor problems with it. It's still a great runnin truck, it's just that knockin that bothers me.

 

could it be exhaust leak or header leak i have a slight leak and it knocks until it gets hot