Engine - Rough Idle/Rich Acceleration/Lean Idle
84pontiac14Number 84-6 (Gasoline)-41B Date 7/84
Subject: REVISED PROCEDURE FOR FUNCTIONAL TESTING OF THE CANISTER CONTROL VALVE -- (APPLICATIONS: 1982-84 CHEVROLET BUILT 5.0 LITER ENGINES.)
When diagnosing a condition such as rough idle, rich acceleration, or lean idle duty cycles (indications of rich carburetion), the following procedure should be followed for diagnosis of a canister control valve:
1. Apply a short length of 3/8" (9.5 mm) I.D. hose to the carburetor bowl tube of the canister control valve (see Figure) and blow into it. Air should pass out through the canister tube. If it does not, replace the canister control valve.
2. Use a hand vacuum pump to apply vacuum (15" Hg or 51 kPa) to the PCV tube. The diaphragm should hold vacuum for at least 20 seconds. If it does not, replace the canister control valve.
3. With vacuum still applied, again try to blow through the hose into the carburetor bowl tube. No air should flow from the canister tube. If it does, the lower valve assembly is not sealing correctly, and the canister control valve must be replaced.
4. Remove the short hose from the carburetor bowl tube, and install it on the canister tube. Move hand vacuum pump to apply vacuum (15" Hg or 51 kPa), to the control vacuum tube, permitting vacuum to raise the upper diaphragm. The diaphragm should hold the vacuum for at least 20 seconds. If it does not, replace the canister control valve. Seal the carburetor bowl tube with a rubber cap or finger, and while vacuum is still being applied to the control vacuum tube, try to blow through the hose connected to the canister tube. Air should pass freely from the PCV tube. If not, canister control valve must be replaced.