I noticed when i start my car, i hear a little knocking but when the motor its getting warm, the knocking gone.
What could it be? 2002 GT

 

i have something like that, i think its normal cus the oil isnt warm and moving around everywhere yet i use 5w30 in mine

 

Your car is going to blow,I'll buy it from you for a $1 LOL

 

There are a few things that it could be...

One would be piston slap, this usually occurs upon initial start up after it sits for a few hours & generally goes away in a matter of a few seconds or in some cases until the engine is warm. If you aren't experiencing any noise when the engine is warm, I would likely blame piston slap. Most times it never becomes an issue & some times it can prove to be catastrophic. I would pinch pennies just to be safe.

 

I have what sounds like exactly the same thing, I have been trying to capture a sound clip of it but whenever I have the camera with me it doesn't do it. It doesnt seem to make a difference how long the car sits for - what causes the pistons to get out of shape like that anyway?

 

It sounds like piston slap which could of been caused by a few things like timing out or assortment or other thing but from the sounds of it i would blame piston slap as the reason like dan said

 

Are you using a Fram oil filter by chance?

If so, very common on some engines. Not sure about the 4.6.

 

+1 for piston slap. If you get a quick rattle when you first start it up then it would be main bearings. I've been through that. When it's cold and you first start the car it'll rattle really fast for a couple of seconds then completely clear up. After a few months of this the rattle will take longer and longer to go away under cold startup until it's knocking all the time.

 

But what if it does not knock on every cold start up - I would say it only knocks during start up about 30% of the time - could it still be piston slap or main bearings?
Also, I don't use a fram filter - heard they were crap.
Thanks

 

Did you buy it used? Previous owner could have slaped forged internals in it. And forged pistons slap or tick till they warm and expand to the walls better. Just a guess.