If your vehicle is showing popping or backfiring sounds from the tailpipe, here are the most likely causes and the parts you'll need to fix each one.
A leak in the exhaust system allows fresh oxygen to get sucked into the hot exhaust pipes. This oxygen mixes with unburned fuel and ignites, causing a popping sound, especially when decelerating. This is highly common after installing aftermarket exhaust components.
Worn spark plugs, failing coils, or bad plug wires prevent the air/fuel mixture from igniting in the cylinder. The unburned fuel is then pushed into the hot exhaust manifold where it violently explodes.
Faulty sensors or leaking fuel injectors can dump excessive fuel into the engine. The engine cannot burn it all, so the raw excess fuel ignites as it travels through the hot exhaust system.
If the engine's mechanical or ignition timing is off, the spark might fire at the wrong time, or the exhaust valves might open before combustion is finished. This sends the combustion explosion directly out the tailpipe. Often caused by a skipped timing belt/chain or a botched timing job.
A burnt, bent, or sticking exhaust valve fails to seal the combustion chamber properly. This allows the explosive force of combustion to shoot directly past the valve and into the exhaust manifold.