"2004 GMC Envoy: The Oxygen Sensor Failure and Engine Knock"

Red 2004 GMC Envoy XUV Front Side

I have a 2004 GMC Envoy XUV, it has started to knock off when I sit in traffic for a long amount of time or when the air conditioning is on, we have put gas treatments in, changed air and fuel filter and cleaned the throttle body. Any clue what is happening with my car?

Answer: It sounds like the Oxygen Sensor or the Catalytic Converter. Usually the “Engine Check Light” will come on, but I have seen situations where there were no warning lights, what-so-ever. If the engine check light is not coming on, have a “Trouble Code Scan” preformed by a qualified mechanic. Because you state that it’s worse when you turn on the air conditioner, or when you’re sitting in traffic, I’m leaning more to the “Oxygen Sensor”. When the air conditioner compressor is turned on, the engine will rev higher, this may cause improper fuel and oxygen mixture. Making the engine knock or feel like it’s going to stall. The GMC Envoy’s oxygen sensor is a critical component for your vehicle. The oxygen sensor monitors the amount of unburned oxygen that is in the exhaust as the exhaust exits the engine. This is an important process for the vehicle as it controls the fuel mixture and regulates the Envoy’s engine performance and emissions. When the Envoy’s oxygen sensor begins to fail or is completely bad, the vehicle’s drivability will be affected and you will notice increased fuel consumption.