reese_melina
New member
The FSM for Altimas natural aspirated engines (there are no turbo Altimas) says that at WOT the pcv valve opening cannot evacuate the blowby because the vacuum is too low downstream of the throttle body ie the air intake pressure downstream of the throttle body is almost at atmospheric pressure. This is easy to understand. However The FSM then states that the blowby at WOT will go the reverse way of the air breather hose. This will then dirty your throttle body if you don't have a catchcan on that side of the valve cover. I understand that the air filter itself creates a small vacuum (because it is a restriction) between itself and the throttle body. However since there is a very little restriction at the throttle body at WOT why isn't the pressure the same from the air filter all the way to the air intake valve? In other words if the blowby doesn't go through the pcv valve at WOT because there is little to no vacuum in the air intake plenum down stream of the throttle body why is the pressure any different between the throttle body and the air intake? I realize that the MAF sensor is also another restriction but the air breather connection is between the MAF sensor and the throttle body. I am confused.