P0303 Fault in 2004 Chevrolet Impala: Diagnosis and Solutions
My 2004 Chevrolet Impala got stuck in snow and I revved the engine, but it did not overheat. Now the check engine light is showing code P0303, and the vehicle runs roughly. I also suspect there might be gasoline odor coming from the dipstick. What steps should I take to diagnose and fix this issue? Please share any advice or troubleshooting tips.
Please confirm which engine variant you have, as cylinder #3 is positioned differently across models. If you don't have a scan tool, start with basic diagnostics for cylinder #3: Is there spark at the plug? What does the plug look like—wet, dry, black, or tan? Perform a fuel pressure leak-down test or use a noid light to check the injector operation (stays on, stays off, flashes?). Try adding a bottle of TECHRON fuel treatment as a potential temporary fix.