Engine Backfires

WARNING: This page is about a different car, the 1995 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.

Ensure proper spark exists from ignition system.
Ensure ignition timing is correct.
Check valve timing and timing belt (if equipped).
Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
Check EGR system.
Check Throttle Position Sensor (TPS) and wiring.
Check oxygen sensor and wiring.