Popping sounds from the rear of the vehicle may be heard moments after starting the engine, or when slowing to a stop. This noise is from the leak detection pump filling the fuel tank with air, and releasing to retest the system when it finds a fault. The sequence of faults identifying this issue are as follows:

Succession of loud pops from rear of vehicle

Pops go away, and fuel economy decreases

Check engine light illuminates

OBD trouble code P2404 and/or P0441is stored

Engine will not start after refueling (must crank for over 30 seconds)

Vibration when slowing to a stop

The cause is a valve which is mounted on the front of the intake manifold, commonly called the N80 valve, or EVAP system purge valve. The valve is designed to open under specific circumstances, but a worn valve will remain open at all times, preventing the pressurization of the fuel tank. Correction of the issue is to replace the N80 valve with the latest revision.

A significant vibration with moderate braking at highway speeds may develop on vehicles stored outdoors for 3 months or more. This condition may be due to corrosion on the brake rotors. Our technicians tell us that normal driving for about a week should eliminate this issue.