Q: Backfiring after the engine is revved up.

Hi there. It is normal for an engine to backfire when revved up and the throttle is let off, especially if the muffler is small and the exhaust is loud. Now, if the engine is backfiring while the engine is being revved up, then the ignition timing is off. This could be the camshaft sensor out of sequence, the timing chain is sloppy and loose, or the spark plugs and wires are in need of replacement. If there is no check engine light, then either the plugs and wires are worn and need replaced or the timing chain is stretched and needs replaced. Us a timing light to see if the timing chain is sloppy by watching the light on the same spark plug number 1. If the light is bounding all over the place on the harmonic balancer, then the chain is stretched and needs replaced. A stretched timing chain and worn plugs may not have the engine light on. If you need further assistance with your engine backfiring, then seek out a professional, such as one from Your Mechanic, to help you.