Symptom Checks

WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2003 Mercury Sable, 2003 Mercury Mountaineer, 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

Check the following items:

Check fuel delivery system. Go to TEST HB: NATURAL GAS FUEL DELIVERY SYSTEM , step 1) (Natural Gas models), or go to TEST HC: GASOLINE FUEL DELIVERY SYSTEM , step 1) (all others) under SYSTEM TESTS in SELF-DIAGNOSTICS - CNG, FLEX-FUEL & GASOLINE article.
Check EVAP emission system for leaks. See EVAPORATIVE EMISSION SYSTEM TESTS in SYSTEM & COMPONENT TESTING - GASOLINE article.
Sulfur content can vary in different fuels. Try a different fuel source.