What to Do When the Engine Malfunction Light Comes On After Adding Poor-Quality Fuel?
2 Answers
After refueling, if the engine malfunction light comes on, it indicates that poor-quality fuel has been added. During the combustion process in the engine, due to the high impurity content and low combustion efficiency of poor-quality fuel, some impurities and unburned fuel accumulate in the combustion chamber, occupying space and subsequently triggering the engine malfunction light. Solution: Promptly drain the poor-quality fuel and clean the fuel tank and fuel lines. After cleaning, refill with high-quality fuel. Besides fuel quality issues, other reasons that may cause the engine malfunction light to come on include: Sensor Malfunction: Sensors such as coolant temperature, crankshaft position, air flow, intake air temperature, and oxygen sensors may be damaged, have poor contact, or experience signal interruption. When the car's ECU cannot accurately obtain engine data, the engine malfunction light will illuminate. Poor Combustion of Air-Fuel Mixture: Poor combustion can lead to engine carbon buildup or knocking. When detected by the oxygen sensor and reported to the ECU, the malfunction light will illuminate as a warning. Issues such as faulty spark plugs, ignition coils, fuel pumps, or clogged fuel lines can cause poor combustion of the air-fuel mixture. Turbocharger Issues: Problems with the intake boost piping or turbocharger can also trigger the engine malfunction light. The most common issue is turbocharger damage, accompanied by symptoms such as oil leaks, excessive oil consumption, reduced power, metallic noises, or blue/black smoke from the exhaust. Intake Issues: If the car's intake system malfunctions, it may lead to clogged engine pipes, and in severe cases, the engine malfunction light will illuminate. A dirty or uncleaned air filter can cause intake problems. Exhaust Issues: Exhaust system faults can also trigger the engine malfunction light. Common causes include faulty rear oxygen sensors, catalytic converters, exhaust camshafts, or bearings. The catalytic converter is most frequently affected. Using leaded gasoline, lead- or silicon-based lubricant additives, physical damage to the catalytic converter, or fuel system malfunctions can easily lead to catalytic converter issues. Anti-Theft System Malfunction: If the car's electronic anti-theft system fails or the anti-theft controller does not match the engine ECU, the anti-theft system can prevent the engine from operating normally, and the engine malfunction light will illuminate.
I've been driving for nearly thirty years and seen too many cases like yours. Don't panic immediately when the warning light comes on due to bad fuel. It might be caused by water contamination or excessive impurities in the gas, clogging the fuel injectors or triggering false sensor signals. My first move would be finding a safe spot to park, avoiding hard acceleration to prevent engine damage. Try recalling where you refueled—was it some cheap gas from a sketchy station? Quickly plan a trip to a reputable repair shop to drain the bad fuel and refill with premium 95-octane gasoline, while adding some fuel system cleaner to flush the lines. The whole fix costs just a few hundred bucks—don’t underestimate it; prolonged neglect could lead to piston seizure or engine knocking, costing thousands to repair. For prevention, I always insist on top-tier fuels like Sinopec at official stations and use regular maintenance with detergents to prevent clogs. Safe driving comes first, and addressing small issues promptly avoids major disasters.
