Chevrolet Equinox Service Manual: Spark Plug Inspection Engine Control

Spark Plug Usage

Ensure that the correct spark plug is installed. An incorrect spark plug causes driveabilityconditions. Refer to the Electronic Parts Catalog.

Inspect the terminal post (1) for damage.Inspect for a bent or broken terminal post-(1).Test for a loose terminal post (1) by twisting and pulling the post. The terminalpost-(1) should NOT move.Inspect the insulator (2) for flashover or carbon tracking, soot. This condition isoften mistakenly identified as a cracked insulator. This is caused by the electricalcharge traveling across the insulator-(2) between the terminal post-(1) and ground.Inspect for the following conditions:Inspect the spark plug boot for damage.Inspect the spark plug recess area of the cylinder head for moisture, such as oil,coolant, or water. A spark plug boot that is saturated causes arcing to ground.Inspect the insulator (2) for cracks. All or part of the electrical charge may arcthrough the crack instead of the electrodes-(3,-4).Inspect for evidence of improper arcing.Measure the gap between the center electrode-(4) and the side electrode-(3) terminals.This must be done carefully in order to avoid damaging the small diameter Iridiumcenter electrode. Refer toIgnition System Specifications. An excessively wide electrode gap can prevent correct spark plug operation.Inspect for the correct spark plug torque. Refer toIgnition System Specifications. Insufficient torque can prevent correct spark plug operation. An over torqued sparkplug, causes the insulator-(2) to crack.Inspect for signs of tracking that occurred near the insulator tip instead of thecenter electrode-(4).Inspect for a broken or worn side electrode-(3).Inspect for a broken, worn, or loose center electrode-(4) by shaking the spark plug.A rattling sound indicates internal damage.A loose center electrode-(4) reduces the spark intensity.Inspect for bridged electrodes-(3,-4). Deposits on the electrodes-(3,-4) reduce oreliminates the gap.Inspect for worn or missing platinum pads on the electrodes-(3,-4) If equipped.Inspect for excessive fouling.Inspect the spark plug recess area of the cylinder head for debris. Dirty or damagedthreads can cause the spark plug not to seat correctly during installation.Spark Plug Visual InspectionNormal operation—Brown to grayish-tan with small amounts of white powdery depositsare normal combustion by-products from fuels with additives. Reddish orange depositscan indicate MMT fuel additive which is still used in some markets around the world(will cause misfire and cannot be burned off). MMT fuel additive use should be avoided.Carbon Fouled—Dry, fluffy black carbon, or soot caused by the following conditions:Rich fuel mixturesLeaking fuel injectorsExcessive fuel pressureRestricted air filter elementIncorrect combustionReduced ignition system voltage outputWeak coilsWorn ignition wiresIncorrect spark plug gapExcessive idling or slow speeds under light loads can keep spark plug temperaturesso low that normal combustion deposits may not burn off.Deposit Fouling—Oil, coolant, or additives that include substances such as silicone,very white coating, reduces the spark intensity. Most powdery deposits will not effectspark intensity unless they form into a glazing over the electrode.