Backfires

SYMPTOM DESCRIPTION
Fuel ignites in intake manifold, or in exhaust system, making a loud popping noise.



SYSTEM OR COMPONENT TO CHECK ACTION



IGNITION CHECK IGNITION COIL for proper output voltage
with spark tester or equivalent (ST-125).
SPARK PLUGS Remove spark plugs,
check for wet plugs, cracks, wear,
improper gap, burned electrodes, or
heavy deposits. Replace as necessary.
SECONDARY CIRCUIT For crossfire between
spark plugs (distributor cap, spark plug
wires and proper routing of plug wires.)
TIMING.



ENGINE CHECK COMPRESSION Perform a compression check,
look for sticking or leaking valves.
VACUUM LEAKS Intake manifold gasket and
hoses.
RESTRICTIONS Intake and exhaust system for
casting flash or other restrictions.



EMISSIONS CHECK EGR operation for being open all the time.

See Exhaust Gas Recirculation. Exhaust Gas Recirculation