Dirty Air Filter

Messages
144
Location
MN
Would it cause increased draw throught the PCV valve, causing the valve to get dirty (oily and sticky) faster? Vehicle is the Kia in my sig. Thanks.
 

possum328

Thread starter
Messages
144
Location
MN
The only thing I have to go on is that I just replaced the PCV valve recently and it seems to be pretty sticky already. Having a hard time finding an air filter for the Kia out here in the sticks... Part 2 -- I would guess that an abnormally high PCV draw would funk up the intake quicker as well?
 
Messages
8,859
Location
Texas
Originally Posted By: possum328
Could it contribute to a rough idle - especially with A/C on?
See IndyLan's post. The throttle plate is 10,000 times more restriction at idle than the dirtiest air filter imaginable. If the air filter could actually be clogged enough to affect idle AT ALL, that would mean that it has become more restrictive than a closed throttle plate and thus the engine wouldn't even run at any speed above idle.
 

possum328

Thread starter
Messages
144
Location
MN
Does it matter that I was wondering if the increased PCV flow would affect idle, not the air filter?
 
Last edited:
Messages
202
Location
California
Any increased PCV flow would be small & negligible. Per 440Magnum's point, I'm pondering the effect of a dirty air filter on PCV flow in an engine that doesn't have a throttle. (BMW has no throttle butterfly.)
 
Messages
163
Location
Tennessee
Bmw no butterfly?????? Really!!!!! My wife's dd is an 09 328i and it has a huge butterfly valve. I know because i've cleaned it. Unless your talking diesel, but any diesel from 04+ has a butterfly valve to work with the egr system.
 
Messages
8,859
Location
Texas
Originally Posted By: possum328
Does it matter that I was wondering if the increased PCV flow would affect idle, not the air filter?
Depends on some specifics of the vehicle. If its a speed-density system that goes into closed-loop mode at idle, then excessive PCV flow will tend to lower MAP, raise the idle speed, and the IAC will close up to compensate, but overall the mixture should remain correct and I wouldn't expect much change in idle quality. If its a mass-airflow system or any system that stays open-loop at idle, then excessive PCV flow will look like a vacuum leak and tend to lean things out, potentially causing idle issues.
 
Messages
8,859
Location
Texas
Originally Posted By: simplistic
Bmw no butterfly?????? Really!!!!! .
The BMW engines with variable-lift valves ("Valvetronic," I think) use the intake valve lift/duration instead of a throttle butterfly to control engine speed. The end result is a lot like Fiat/Chrysler Multi-Air, though the implementation is completely different.
 
Messages
163
Location
Tennessee
On the wife's bmw it has that double vanos and the valvetronic. I did read up on this after your post... then I have a question. Why put a throttle body w/butterfly valve if it's not need?
 

possum328

Thread starter
Messages
144
Location
MN
UPDATE (for whoever is still following...) I replaced the very dirty air filter, as well as the front 3 spark plugs. The rough idle is gone. Thanks.
 
Messages
3,681
Location
ks, wichita
in the ARMY we had very big diesel engines. they had a dirty air filter indicator on the dash. the air filter was about 2 ft in dia. have NEVER seen one on a car / pick up.
 
Messages
1,054
Location
Wash, DC
I imagine a military vehicle may find itself in a convoy on a dusty dirt road; and the filter could clog up quick enough to justify a restriction meter.
 
Top