22re is backfiring in the exhaust during acceleration. There is no noticeable loss of power when the backfire occurs. It seems to be getting worse and I have gone thru several mufflers in the last 2 years. Anyone know what could cause this problem.

 

After fire, is usually unburnt fuel hitting a hot spot (flow resistiction).

Valve leak, drop the exhaust at the manifold lower connection and seafoam it.

Or

Time for a new oxygen sensor.

 

Tight, or burned exhaust valve??
Any recent valve lash adjustment??