using breather cap
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The ECM will think you have a vacuum leak (which you do have).
The normal routing of CCV air is from the throttle body. That air is measured by the MAF. The air goes through the crank case and the PCV valve and into the intake manifold, so it does affect the AFR.
The normal routing of CCV air is from the throttle body. That air is measured by the MAF. The air goes through the crank case and the PCV valve and into the intake manifold, so it does affect the AFR.
Thread Starter
Instructor
Joined: Jul 2007
Posts: 112
Likes: 3
From: Pace fl
That's what I thought. I got a cap with a nipple and run the line to the throttle body. My mpg went up 2 miles per gallon in one trip back and forth from work. About 20 miles each way.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
I thought it only allowed one way air flow through the breather port on the throttle body? At least mine is that way.
Safety Car
Joined: Nov 2009
Posts: 3,973
Likes: 341
From: Adelaide South Australia
As Cliff explained the whole of the PCV system is set up to drag the "dirty" air out of the crankcase and into the intake to be burnt up by the engine.
with a MAF engine you need to take the fresh air into the crankcase AFTER the MAF has measured it.
your engine oil also benefits from having contaminants sucked out.
One thing I have learnt (after some research from others experience) is that the L98 plenums get oily and dirty from the throttle body (into crankcase) line having no one-way or check valve in that line. I even noticed that my new intake elbow had an oily residue in it after a short time. I fitted a PCV valve into the intake line as well so air can only flow from the throttle body into the crankcase. My intake plenum is always clean now.
with a MAF engine you need to take the fresh air into the crankcase AFTER the MAF has measured it.
your engine oil also benefits from having contaminants sucked out.
One thing I have learnt (after some research from others experience) is that the L98 plenums get oily and dirty from the throttle body (into crankcase) line having no one-way or check valve in that line. I even noticed that my new intake elbow had an oily residue in it after a short time. I fitted a PCV valve into the intake line as well so air can only flow from the throttle body into the crankcase. My intake plenum is always clean now.
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