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Have you ever been driving and noticed a loud pop from behind? Engine backfires are commonly associated with older trucks, but can happen with any vehicle. Sometimes Engine backfires indicate that you may have a massive mechanical issue. 

What causes engine backfires? 

Engine backfires occur when an internal combustion engine produces an explosion or combustion happens in the exhaust instead of the combustion chamber. 

A backfire or afterburn refers to a fuel burn while the air valve intake is open, causing the fire to move backward out of the intake system instead of the exhaust. 

So, an electric car can’t backfire. Also, modern engines have variable valve timings and computer-controlled spark timing to mostly prevent backfires. But if you think your engine is backfiring, then it could be a sign of a much larger issue. 

For example, lean air-fuel mixture is a common cause. By not having enough fuel in the engine, not enough of it mixes with air then the combustion process slows down. 

When the gas valves open, unburned fuel can enter the exhaust. This issue is related to failing fuel pumps, clogged injectors, or a fuel leak in the pressure system. 

A dual car exhaust with smoke
Engine backfire | iStock

Also, a rich air-fuel mixture can lead to a backfire. The sparks need to fire and the valves need to close at the right time. 

If too much fuel is added to the engine it can dump into the red hot exhaust and combust. This may be related to leaking fuel injectors or faulty engine sensors. 

Bent or damaged valves are another source of backfires. Valves need to open and close before the pistons rise. But if the engine timing is off, the pistons can strike the open valves, resulting in a faulty seal that requires significant engine repairs to correct. 

Bad ignition timing may prevent the intake and exhaust valves from opening and closing at the correct times. They open hundreds to thousands of times per minute. 

If the intake valve doesn’t close in time, fuel could leak into the engine manifold. If the exhaust valve opens too early, unspent fuel spreads into the exhaust and can emit flames. 

So, don’t ignore engine backfires. They may indicate that you have a fuel leak, failing fuel injectors, or much larger engine problems.