Which symptom indicates a potential fuel metering issue during idle?

• A. Smooth idle with constant AFR
• B. Rough idle with AFR fluctuations and potential misfires
• C. No exhaust
• D. Overheating engine

Answer: (B)

During idle, the engine relies on precise fuel metering to keep the air–fuel ratio steady so the engine runs smoothly. If the metering starts to fail, the air–fuel ratio won’t stay constant, causing the engine to stumble and misfire as some cylinders get too much or too little fuel. That combination—rough idle with fluctuations in AFR and potential misfires—is a clear sign of a fuel metering issue at idle. A smooth idle with a steady AFR means the metering is working correctly. No exhaust or overheating aren’t direct indicators of a metering problem at idle.