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I am tracking down a vacuum leak and I have narrowed it down to the emissions side of the vacuum system. Does anyone know how the valve pictured below is supposed to work I have searched but I have not found a thread on how this valve works? I just bought this used unit as I thought the old unit was bad.
Problem
I get a strong vacuum from the intake side (top hose) and that vacuum pressure is consistent on at the attachment for the bottom hose, no amount of vacuum on the port will change the vacuum on the bottom hose. There must be some type of function on this valve if it is full open no matter what I am guessing I could just delete it. The valve off the charcoal canister attached to the thermal vacuum switch works as it should and the valve will open when the throttle is opened. The car runs perfect when cold but when it is warm a vacuum leak becomes present.
Your valve is defective. That valve should be closed when full manifold vacuum (17"-20") is applied and open wider as manifold vacuum drops (i.e. as the throttle opens). This valve controls the volume of fuel vapors from the charcoal canister to the manifold (more flow as the throttle opens wider, less flow with less throttle.) The valve connected between this one and the charcoal canister is the on/off valve for the system. It only opens when the throttle plate is opened just past the idle stop, ensuring there is no flow of fuel vapor at idle which would lead to an over-rich idle mixture. The valve is available new ( 944 part number) but hold on to your wallet.
I was about to suggest that you do as many of us do and simply cap off the the system. You are, however, a resident of California.
This is good information nonetheless, as the function of the mystery strut bar valve was previously unknown to me. The valve before it, located near the inner fender, failed on my car and led to a collapsed fuel tank.
Thank you. I have another new to me valve on order, hopefully #2 is the charm. Tracing down this vacuum leak has being a huge PIA, I took apart the intake twice and tried using a few fireball methods of finding the leak with no success. This is the only valve left that isn't brand new, it would pain me to have to spend 1/4 of the purchase price on a new valve.
08-31-2018, 01:20 AM
A/C Idle Valve - EVAP System - Charcoal Cannister
