Hmmmm, ive been listening to this off and on for 2 or 3 weeks now and its making me nervous. So far I have only heard this knocking sound on cold start up in the mornings. Also, if I rev the motor up it will still have the knock. To describe what it sounds like.........kind of like hitting a nail into a block of wood with a hammer. But not overly loud, fairly quiet so far Does this sound like a rod knock??? At first when I heard it I thought it was impossible, I have roughly 99,000 miles which is fairly low to be having severe lower engine problems with a fuel injected engine. Any thoughts?

Im just glad I am doing an engine swap next spring if this does in fact turn out to be an engine knock.

90 f-150
5.0EFI 5 speed
4x4 4" superlift 33" MT duelers

 

My guess is rod knock. But since we can't hear it, it could be something else. Mine knocks for around 10 secs on some mornings, not at all on other mornings. Its been doing it since shortly after I bought it, Almost 2 years now. It hasn't gotten worse.

(My theory with my truck);
Whenever I use NAPA Gold filters it doesn't knock. Seems to knock more often when I use Wix. whats the diff? I don't know.

 

I just talked to buddy of mine who listened to my truck. He said his inline 6 did it to and he thought it had something to do with the fan belt. However, I am almost sure it sounds like its comming from the lower unit. I could also hear it slightly when I opened the hood this afternoon. He called it a ticking but to me it sounds more like a knock.