How does a faulty injector affect engine combustion stability?

• A. It improves throttle response
• B. It eliminates emissions completely
• C. Uneven fueling causes misfires, AFR fluctuations, rough running, loss of power, and catalyst damage
• D. It only affects oil consumption

Answer: (C)

Fuel injectors must deliver precise amounts of fuel to each cylinder at the right time. When an injector is faulty, that balance is lost, and fueling becomes uneven across cylinders. Some cylinders may receive too much fuel (rich), others too little (lean). This mismatch disrupts combustion stability, leading to misfires, fluctuations in the air-fuel ratio, rough idle or running, and a noticeable drop in power. Misfires and improper mixtures also strain the catalytic converter, since unburned or overly hot exhaust can damage it over time. The other options don’t fit the reality of what happens: a bad injector doesn’t improve throttle response, can’t make emissions vanish completely, and its most visible effect isn’t limited to oil consumption alone.