why does my Toyota Highlander Third Generation (2014-2019) make a hissing sound when driving

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical hazards.

2. Inspect and Replace Vacuum Hoses

• Tools Required: Pliers, socket set, screwdriver.
• Check all vacuum hoses for cracks, wear, or disconnections.
• If any hose is damaged, cut the old section out and replace it with a new hose of the same diameter.
• Secure the new hose with clamps.

3. Throttle Body Gasket Replacement

• Tools Required: Socket set, gasket scraper, torque wrench.
• Remove the air intake duct to access the throttle body.
• Unbolt the throttle body from the intake manifold.
• Carefully remove the old gasket and clean the mating surfaces.
• Place a new gasket onto the throttle body and reattach it, torquing bolts to manufacturer specifications (usually around 89 in-lbs).

4. Inspect and Clean PCV Valve

• Tools Required: Pliers, cleaning solvent.
• Locate the PCV valve and remove it from the engine.
• Inspect the valve for debris and ensure it moves freely.
• Clean it using a solvent if dirty, or replace it if malfunctioning.
• Reinstall the PCV valve, ensuring it is seated properly.