Engine Backfires
- Check for excessively lean air/fuel mixture.
- Check for an air intake leak. Idle speed will usually be faster if an intake air leak is present.
- Check for leaking air into or out of the exhaust system.
- Check for air leakage past valve guides or valves.
- Check for ignition timing retarded.
- Check for incorrect valve timing.
- Check for valves sticking open.