GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firefly (Canada) 🢒 Engine 🢒 Engine Controls - 1.0L 🢒 Backfire

Checks

Action

DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.

Preliminary Check
    • Refer to Symptoms .

Ignition System Checks
    • Check for adequate ignition coil voltage with a J 26792 spark tester or equivalent.
    • Check the spark plugs for any of the following conditions:
       - Wet (fuel fouled) plugs.
       - A terminal screw that is bent or loose (rotate and pull).
       - A ceramic insulator that has cracks, carbon tracking or deposits (red or black dust).
       - A tip insulator that has cracks, carbon tracking, deposits (oil, carbon, glazing, fuel additive), or is loose (rattles).
       - A center electrode that is loose (wiggles side to side).
       - An incorrect spark plug gap that is too large or too small.
       - Platinum pads that are missing.
    • Check the ignition timing. Refer to Ignition Timing Adjustment .
    • Check for crossfiring between spark plugs (distributor cap, spark plug wires, and proper routing of plug wires).

Engine Mechanical Checks
    • Check for any of the following engine mechanical problems:
       - Faulty hydraulic lifter assemblies
       - Broken or weak valve springs
       - Low compression
       - Sticking or leaking valves
       - Incorrect valve timing
       - Incorrect or worn camshaft
    • Refer to Engine Compression Test in Engine Mechanical.
    • Check the intake and exhaust system for casting flash or other restrictions.

Additional Check

Check the EGR Valve for being open all the time. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis .