What Causes a Rich Fuel System?

[JasmineRose]

Fuel system running rich may result from the following causes: High fuel mixture ratio: The engine's fuel mixture is too rich due to possible minor injector leakage, faulty coolant temperature sensor, or potential malfunctions of the mass airflow sensor and oxygen sensor. Insufficient cylinder pressure: Low compression pressure in engine cylinders with too small a compression ratio can be audibly detected during performance checks. If uncertain, measure cylinder pressure directly. Low cylinder pressure typically indicates mechanical issues such as problems with pistons, rings, cylinders, or valves. Weak high-voltage ignition: Causes include spark plug carbon buildup, narrow electrode gaps, poor performance characteristics, or electrical leakage leading to misfires.