I have a 96 EX with the F22B1 4-cyl VTEC engine. I recently bought and installed an aftermarket PCV valve for $3 from the local Autozone and would like to make sure it's working completely. We've had an off-and-on issue with oil seepage through the main seals (before and after this new PCV valve) so I would like to confirm if the PCV valve is doing it's job with respect to crankcase pressure.

Here's what I tested:

* Engine warmed up, low idle speed. Idle is smooth and pretty quiet ... very faint valve tap noise -- not PCV valve clicking as far as I could tell.

* Squeezed PCV hose, engine idle slowed down noticably, but did not stall. However I did not hear the clicking sound from the PCV valve as I squezed the hose.

* Pulled PCV valve off of valve cover:
- put finger up against opening of PCV valve, felt moderate suction
- felt opening of valve cover, sputting of air blowing out, similar to blowing through a straw. No oil or smoke color, just clear air.

What I did not check:
* shake pcv valve to hear rattling sound. Not sure if this should be done with the engine running and suction going through the valve, or engine off.
* with PCV valve installed, check suction through oil filler cap hole.
* trying higher rpms

Any interpretation of the above test results and suggestions for further testing would be much appreciated. Question I have:

1) Should I have heard a clicking sound when I squeezed the tube?

2) Is the air sputtering out of the valve cover normal? It seems like the PCV would have to suck in a lot of air in order to keep the crankcase at neutral or vacuum air pressure.

3) My understanding of the valve operation is that at low idle when manifold vacuum is high, the valve actually closes, either all or partially. At higher rpms when the manifold vacuum is low, the valve opens up all the way to allow better crankcase breathing. Is there a way I can confirm the suction levels through the valve at low and high rpms? And should I still feel suction at low idle?

4) Are there any known differences betwen aftermarket PCV valves and the ones you get from the dealership (other than 8x the price)? It sounds like the pressure threshold is pretty important for correct operation ... however since

Thanks. John

 

1) Should I have heard a clicking sound when I squeezed the tube?
Response: Yes, but you may need pliers to rapidly pinch the hose closed. Also some PCV's are plastic and plastic valve movement will make very faint click.

2) Is the air sputtering out of the valve cover normal? It seems like the PCV would have to suck in a lot of air in order to keep the crankcase at neutral or vacuum air pressure.
Response: Yes, sputtering is normal. This is pulses of piston blowby that occur w/ engine combustion. PCV does pull a lot of air in but poor engine rings can allow blowby to overwhelm the PCV system. Even w/ engine in good shape, reverse flow out the PCV air intake to the air intake duct occurs with heavy acceleration.

3) My understanding of the valve operation is that at low idle when manifold vacuum is high, the valve actually closes, either all or partially. At higher rpms when the manifold vacuum is low, the valve opens up all the way to allow better crankcase breathing. Is there a way I can confirm the suction levels through the valve at low and high rpms? And should I still feel suction at low idle?
Response: Opposite your description. When engine is at idle or steady engine speed (max vacuum level) the PCV will open to allow crankcase gases to be pulled into the engine and burned. Air flows from air intake to crankcase to maintain vacuum level. When acceleration occurs, vacuum is low and crankcase pressure will increase and shut PCV. Crankcase excess flow goes into air intake duct.

4) Are there any known differences betwen aftermarket PCV valves and the ones you get from the dealership (other than 8x the price)? It sounds like the pressure threshold is pretty important for correct operation ... however since
Response: PCV's are not rocket science and I've not heard of any problems w/ aftermarket PCV's. It would be a simple engineering task to duplicate the factory PCV.

good luck

 

Okay, I'm learning more as I look around ... please take a look at this web page:

PCV Valve Problems: PCV Function and Operation

I would think it makes sense that at higher rpm you want more breathing to avoid pressure buildup in the crankcase?

Wikipedia also says essentially the same thing, http://en.wikipedia.org/wiki/Pcv_valve, with the added mention of a backflow preventer.

Thanks. John

 

It depends whether you're accelerating or steady rpms. You get high vacuum w/ steady rpms, at idle and at speed. When accelerating, vacuum is low.

good luck