Jeep Cherokee

 Service Manual

Ignition system » Description and operation
Spark plugs

DESCRIPTION

Resistor type spark plugs are used.

Spark plug resistance values range from 6,000 to 20,000 ohms (when checked with at least a 1000 volt spark plug tester). Do not use an ohmmeter to check the resistance values of the spark plugs.

Inaccurate readings will result.

OPERATION

To prevent possible pre-ignition and/or mechanical engine damage, the correct type/heat range/number spark plug must be used.

Always use the recommended torque when tightening spark plugs. Incorrect torque can distort the spark plug and change plug gap. It can also pull the plug threads and do possible damage to both the spark plug and the cylinder head.

Remove the spark plugs and examine them for burned electrodes and fouled, cracked or broken porcelain insulators. Keep plugs arranged in the order in which they were removed from the engine. A single plug displaying an abnormal condition indicates that a problem exists in the corresponding cylinder.

Replace spark plugs at the intervals recommended in Group O, Lubrication and Maintenance Spark plugs that have low mileage may be cleaned and reused if not otherwise defective, carbon or oil fouled. Also refer to Spark Plug Conditions.

CAUTION: Never use a motorized wire wheel brush to clean the spark plugs. Metallic deposits will remain on the spark plug insulator and will cause plug misfire.

Ignition system

Distributor-2.5L engine

Spark plugs

Spark plug cables-2.5L engine

Ignition coil-2.5L engine

Ignition coil-4.0L engine

Crankshaft position sensor

Camshaft position sensor-2.5L engine

Camshaft position sensor-4.0L engine

Ignition switch and key lock cylinder