If engine stall, hesitation, increase fuel consumption or lack of power is experienced with vehicle, check all vacuum lines for connection, cracks or loose fitting and proper routing. Replace or reroute as necessary.
To check vacuum motor, stop engine and unhook fresh air duct. Using a mirror, check position of air control valve inside duct. With engine warm, fresh air inlet should be open and hot air duct closed. Check control valve linkage.
Disconnect vacuum motor inlet vacuum hose. Install another length of hose to inlet and apply vacuum through this hose to vacuum motor.
With vacuum applied, again use mirror to check air control valve position. Fresh air inlet should now be closed and hot air inlet open.
With hot air inlet open (vacuum still applied), pinch vacuum hose to cut off air to vacuum motor. Air control valve should hold position for more than 30 seconds.
If force of diaphragm spring overcomes vacuum and opens fresh air inlet in less than 30 seconds, replace vacuum motor assembly.
To check temperature sensor, start and idle engine. As engine warms up, air control valve should slowly open to admit fresh underhood air. Ensure that air control valve moves up and down with increase or decrease in engine speed.

Fig 1: ATC Vacuum Motor

Courtesy of NISSAN MOTOR CO., U.S.A.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

ATC System: Notes