PCV system

[stanno]

Hi all;

I'm trying to understand the pcv system on my jdm 3sfe.

My engine didn't come equipped with an egr system. But on other cars i've ever seen, they have a breather on the VC for fresh air to be drawn into the crankcase and then a second breather port that usually go to the IM, to recycle those vapors.

On my 3s, i see no breather, just one port on the VC that has a hose connecting to the IM.

I pulled off the hose with the engine idling, and there was air pulsating from it, NOT vacuum. There's also oil puddled in the IM where the port from the pcv is.

Is this normal?

[white90dx]

You aren't quite right about the 'normal' setup with mutiple breathers. In most cases, if an engine has multiple breathers, they are pulling air out of the motor. In some operating modes, a breather may pull fresh air into the motor, but it is mainly there to let air out of the crankcase.

Blowby around the pistons in the motor will create the pulsing you describe. Some amount is normal and expected. The 3s-fe has a very simple setup with just a hose with no valve from the intake manifold to the valve cover. The oil you see is due to a small amount of oil vapour suspended in the air in the crankcase being sucked into the intake manifold.

-Charlie

[stanno]

Originally Posted by white90dx

You aren't quite right about the 'normal' setup with mutiple breathers. In most cases, if an engine has multiple breathers, they are pulling air out of the motor. In some operating modes, a breather may pull fresh air into the motor, but it is mainly there to let air out of the crankcase.

Blowby around the pistons in the motor will create the pulsing you describe. Some amount is normal and expected. The 3s-fe has a very simple setup with just a hose with no valve from the intake manifold to the valve cover. The oil you see is due to a small amount of oil vapour suspended in the air in the crankcase being sucked into the intake manifold.

-Charlie

Ok, so blow by may cause the pulsating at idle. If it were blow by, would that pulsation still be present when rpm is increased ?

Reason i asked is cuz when i do increase rpm, the pulsation subsides, but, i don't really feel any vacuum.

I'm wondering now if this is the cause of the misfiring in my engine. With the engine idling, i can hear puffing from the tailpipe and sometimes i can hear the engine making popping noises at idle also... suggesting a misfire

[white90dx]

Originally Posted by stanno

Ok, so blow by may cause the pulsating at idle. If it were blow by, would that pulsation still be present when rpm is increased ?

Reason i asked is cuz when i do increase rpm, the pulsation subsides, but, i don't really feel any vacuum.

I'm wondering now if this is the cause of the misfiring in my engine. With the engine idling, i can hear puffing from the tailpipe and sometimes i can hear the engine making popping noises at idle also... suggesting a misfire

I think you are confusing some terms or something...

If you pull the crankcase vent tube off while the engine is running, you are supposed to feel air puffing/pulsing out. It vents to the intake manifold to keep emissions down and keep the engine 'closed' so the AFM meters air correctly. There will never be vacuum coming from the engine side, and there should always be vacuum on the intake manifold side.

The pulsing subsides at higher RPM because the indivual pulses are too closely spaced to feel (each combustion event makes a pulse).

"Puffing" out the tail pipe at idle is normal. The little pops do suggest that there is a misfire, but that is separate from anything else.

-Charlie

[stanno]

Originally Posted by white90dx

I think you are confusing some terms or something...

If you pull the crankcase vent tube off while the engine is running, you are supposed to feel air puffing/pulsing out. It vents to the intake manifold to keep emissions down and keep the engine 'closed' so the AFM meters air correctly. There will never be vacuum coming from the engine side, and there should always be vacuum on the intake manifold side.

The pulsing subsides at higher RPM because the indivual pulses are too closely spaced to feel (each combustion event makes a pulse).

"Puffing" out the tail pipe at idle is normal. The little pops do suggest that there is a misfire, but that is separate from anything else.

-Charlie

Thanks for clearing that up.