Just curious if anyone on here has operated like this for any period of time. I've run muscle cars like this in days gone by, and while testing an erratic idle problem on my 2002 Escape 3.0, I did this...

- Removed the PCV line from the rear of the manifold and left it vented to atmosphere

- Capped the associated port on the back of the manifold where the PCV hose connected

- Opened the two valve cover ports (that connect to the intake tube, downstream from the MAF) to atmosphere and plugged the "T" inlet to the intake tube.

I'm aware that the PCV system is a closed loop (well, except for the gases that are pushed into the crankcase by the pistons). Fresh air is metered into the crankcase downstream from the MAF through the valve covers while it's being drawn in by intake vacuum via the PCV valve, that way is is accounted for by the MAF.

Idle is perfect in this setup. Probably nothing to be gained in this configuration, it was just part of my test to verify that the PCV circuit was my uneven idle culprit. The crankcase doesn't build pressuse, as it's all open to atmosphere. Just wondering if anyone has been operating in this manner.

Dave

 

What you are describing it the pre-1963 open blowby or road-draft system. The PCV system is open to the atmosphere as was common until about that point in time.
If you have a leaky system, you'll get extra air ingesed that the MAF doesn't account for, and possibly a flaky idle. If that was the problem, take a look if you haven't already done so, at the elbow on the rear side of the intake.
tom

 

Hi Tom,

Yeah, I corrected the elbow issue on the back side of the intake some time ago, but the flakey idle crept back in recently. I couldn't see the elbow at the pcv valve, but I think it must be bad or collapsing, too. When I did this as a test, the idle is perfect again. Running it a couple of days like this to make sure that's the deal. The piping on the top side that goes from the valve covers to the intake tube looked OK and were not leaking. If there is no problem with the elbow at the PCV valve, there must be a crankcase leak somewhere else, though I can't imagine where...

Dave