hello, my car has had a engine noise lately and i had received a code for a new knock sensor when my oxy sensor triggered my check engine light. My friend took a look at it today and we observed these conditions:

-we opened the oil cap and A LOT of air flew out of the engine.
-made me rev the car and pointed out how the air out of the exhaust isn't consistent.
-said that the engine knocking could be my vacuum lines.

Anyone have any tips or ideas what could cause this engine knocking noise or if there is something i can do to check these things out? I notice when i start my car and i hit drive or reverse (i have an auto...sucks...) i hear some sort of air or liquid flowing through my engine causing a whish noise of some sort. any ideas? any help would be greatly appreciated!!

EDIT- sorry completely blew my mind. I have a 240sx KA engine stock. It is a 1996 model

 

I'm not sure, but I think that might be a blown headgasket.

 

its not leaking oil a lot. it is leaking a little bit though. So, i dunno if it can be a blown headgasket, plus no mixture of oil with coolant so i dunno if it is the headgasket but does anyone else have any other suggestions? someone told me to turn the engine on, and pull out the spark wire thats in the engine and go through each cylinder to see if the noise changes in any form. He said it might be the rod?

 

It may be the oil pressure or your pistons are hitting the wall of the cylinder....you might want to check google

 

Are you over-heating?

 

It doesnt have to leak oil if you blew the headgasket. It could have blown between the cylinders. then when it is running, it would push the air it was trying to compress out the other cylinder. Like I said, Im not sure, but that is a possibility.

edit:also check the PCV valve and the breather hoses for the valve cover and make sure the PCV is functioning properly and the breather hoses are not plugged. That would trap air in the head and not let it escape to where it needs to go.

 

hmmm i wen to a website and it gave me an audio link for a piston slap, and that is what it sounds like... anyway ok replace the pcv valve? my friend is bringing a fuel guage this week and will check it out cuz he thinks its a vacuum issue. we will see, but anyone else have any other ideas or suggestions? thanks.

 

oh, and it is not overheating, what should i search under google? low oil pressure?

 

I dont think it is piston slap..Piston slap mostly occurs during the first few minutes of idle when the car is started..If it goes away after a couple minutes then u might have to get a new gasket

 

if it makes a noise when u rev it could be rod berrings are bad caused by low oil pressure. and the air in the head sounds like pcv valve