I tested my PCV by taking off the oil fill cap and placing a piece of paper over it. I observed a pulsating suction and not a constant suction. Is that normal? If it's normal should I clean the PCV anyways since it's probably never been cleaned in 17 years?


1 Answer 1


The pulsing should not be a huge issue. Remember that your 4-cyl engine will not have a constant vacuum associated with it as it is only drawing it twice per revolution of the crankshaft, which means you'll get vacuum pulses. Vehicles with more cylinders will have a more constant vacuum draw, but will still have vacuum pulses ... they'll just be less noticeable.

You can do some checks on your PCV to ensure there's no issue with it. I found a couple of videos which might help.

First this one ... just watch the first minute or so of this one. The rest is kind of blah-blah-blah -- it isn't bad information, I just don't know that it's pertinent to your question at this point. (IOW: Watch at your own risk, lol. It isn't too long, so not a big deal.)

Second this one ... this one is short and sweet. The guy gives the universal way to check your PCV.

Basically what you are looking for in the PCV is if you hear the rattle. It is easily cleaned with some carb cleaner. Just take it off and spray it down. If you still don't hear the rattle, replace it with an OE (Mazda) replacement part. It's cheap, (under $4 here in the States) so shouldn't dent the wallet. Also, while the vehicle is running, pull the PCV out of the valve cover (or where ever it's located) and put your thumb over the opening. You should feel suction on your thumb and there should be a noticeable drop in RPM when you do so. If you hear the rattle and you aren't feeling much suction, check the hose to ensure it isn't cracked or leaking.

  • So I checked the PCV valve itself and there was constant suction there and I could hear a bit of a rattle when I shook it. When I would press in the plunger it springs back out, but it looked very cruddy so I got some degreasing foam spray and sprayed it into the PCV to try and degunk it a bit. I'll have to wait and see if it makes any difference. Feb 4, 2015 at 14:36

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .