The combination air control/bypass valve combines the secondary air bypass and air control functions. The valve is located in the air supply line between the air pump and the upstream/downstream air supply check valves.
The air bypass portion controls the flow of thermactor air to the exhaust system or allows thermactor air to be bypassed to atmosphere. When air is not being bypassed, the air control portion of the valve switches the air injection point to either an upstream or downstream location.
- Turn the ignition key OFF .
- Remove the hoses from the combination air control valve outlets A and B and inspect the outlets for damage from hot exhaust gases.
- If the valve appears damaged, replace it, then check the air check valve. If the valve is not damaged, proceed to Step 4.
- Leave the hoses disconnected from the valve. Disconnect and plug the vacuum line to port D.
- Start the engine and run at 1500 rpm. If air flow is present at the valve, proceed to Step 6. If it is not, check the air pump. If the air pump is okay, replace the combination air control valve.
- Leave the engine running. Disconnect both vacuum lines to ports D and S.
- Measure the manifold vacuum at both ports. If the proper vacuum is present, proceed to Step 8. If not, check the solenoid vacuum valve.
- Turn the ignition key OFF . Reconnect the vacuum line to port D, but leave the vacuum line to port S disconnected and plugged.
- Start the engine and run it at 1500 rpm. If air flow is present at outlet B, but not at outlet A, proceed to Step 10. If not, replace the combination air control valve and reconnect all hoses.
- Turn the ignition key OFF and leave the vacuum line to port S disconnected and unplugged.
- Apply 8-10 in. Hg of vacuum to port S on the combination valve. Start the engine and run at 1500 rpm. If air flow is present at outlet A, the combination valve is okay. If not, replace the combination air control valve.
If the combination valve is a bleed type, this will affect the amount of air flow.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Disconnect the air hoses and vacuum lines from the valve.
- Remove the valve from the vehicle.
- Installation is the reverse of the removal procedure.