intermittent PCV vacuum leak

[dlb]

after messing around a bunch, i finally found that the PCV is the cause of my intermittent high idle problem in my corolla (first detailed here: viewtopic.php?f=4&t=11753). the PCV valve was actually my first suspect since the old valve appeared marginal when i tested it, but i replaced the valve with a new one and the problem remained so i moved on and inspected the EGR and brake booster systems. i disconnected both of those and did some driving (VERY careful, slow driving with the power brakes disconnected, yikes) and found the high idle problem remained. so tonight i tried disconnecting the PCV hose from the intake plenum and plugged the port, leaving the PCV hose open to atmosphere. ta da, no more weird idle issues. great.

but now i'm not sure how to fix this. why did the brand new PCV valve not solve the issue? is there too much blowby pressure in the crankcase or too much vacuum in the manifold? neither seems likely -- i have a vacuum gauge installed to temper my lead foot and manifold vac is routinely around 19-20" at idle, and i did a compression test when i first got the car that showed all the cylinders at about 195 psi. i've done regular oil and filter changes every 5000 km (3000 miles) since then so i can't imagine the rings or valves have worn significantly, allowing tons of blowby gases to increase the crank case pressure. but i will do another compression test tomorrow just to make sure.

if anyone has any other ideas on why the PCV system is causing me this issue, i'm all ears.

[rocketscience]

Is the PCV valve grommet in good shape? Mine was hard as a rock and broken when I replaced the valve. Are you sure the new valve works correctly?

[dlb]

yup, the grommet is in good shape. i tested the new valve and it works as it should.

[Petros]

some times even new parts are junk out of the box. might try a different brand of valve, they do not cost much. You might as a test swap one out from one or your other cars, presuming they are similar enough to work okay.

[irowiki]

Did you actually replace the grommet?

How's the hose going from the PCV to the intake manifold? Is it sealing on the intake manifold end?

[dlb]

no, i did not replace the grommet because the valve is still a very snug fit in it. but beyond that, i don't think a loose fit between the valve and grommet would cause much in the way of a vacuum leak since the hose from the manifold is still snugly secured to the valve, which means the manifold is only getting what the valve is allowing in -- whether it's letting ambient air or crankcase gases in, i don't think it would make much difference. the end result is still a carefully metered i think the biggest problem with loose grommets is oil seepage on the valve cover. but anyway, the valve is snug in the grommet.

the hose is in good shape. snug at both ends.

i'm going to town today so i'm going to try a few things, including getting another PCV valve. the one i put in the other day is some aftermarket brand i can't remember so i'll try one from toyota.

[rocketscience]

Did you find the source of the leak?

[dlb]

not yet. but after spending $18 on a god damn genuine toyota PCV valve, i learned that it was the not cause of the problem. the problem is intermittent but tends to occur only after the engine gets up to normal operating temperature. so i'm tracking it down and have determined it is not a vacuum leak, and am currently leaning towards a faulty vacuum switch or a faulty water temp switch. i'll post what i find once i solve it.

[irowiki]

not yet. but after spending $18 on a god damn genuine toyota PCV valve

This made my morning