This system is used on the 4M engine to improve driveability. It cuts air supplied to the main nozzle of the carburetor under certain conditions to improve performance.
If the system is suspected to be operating improperly, test the Vacuum Control Valve (VCV) as described below. If any of the tests are failed, replace the valve.
- Disconnect hoses 10 and 15 at the carburetor. Start the engine.
- Blow air into hose No. 10 at idle speed. Check to see that air is expelled from hose 15.
- Connect the VCV S pipe to the intake manifold as shown in the illustration. Again, blow air into hoses 10 at idle speed. Check to see that air comes out of hose 15.
- Stop the engine. Again blow air into hose 10. Check to see that air does not come out of hose.