For 1990-2009 cars

Checks | Action
--- | ---
DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.
Preliminary Check |

• | Refer to Powertrain On Board Diagnostic (OBD) System 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 .