Checks
| Actions
|
DEFINITION:
Fuel ignites in the intake manifold or in the exhaust system, making a loud
popping noise.
|
Preliminary Checks
|
| • | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
| • | Inspect the powertrain control module (PCM) grounds for being
clean, tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
|
Fuel
System
|
| • | Inspect that each injector harness is connected to the correct
injector or cylinder according to the firing order. Relocate injector
harnesses as necessary. |
|
Sensor/System
|
| • | Inspect the air intake system and the crankcase for air leaks. |
| • | Test the crankcase ventilation valve for proper operation. Place
a finger over inlet hole in valve end several times. The valve should snap
back. If not, replace the valve. |
| • | Inspect for proper calibration of the speedometer. Connect the J 33431-B
signal generator to
the vehicle speed sensor (VSS) electrical connector. Turn ON the ignition,
the tester, and monitor the speedometer. The speedometer should
indicate 86 km/h (54 mph). If not, refer to Gauge
System Check. |
|
Ignition System
|
| • | Test for proper ignition voltage output with the J 26792
spark tester. |
| • | Inspect for an intermittent ignition system malfunction in the
following circuits: |
| - | Ignition control circuit |
| - | Use the Snapshot feature on the scan tool in order to help locate
an intermittent ignition failure. |
| • | Remove the spark plugs and inspect for the following conditions: |
| • | An improper spark plug gap causes a driveability concern. Gap
the spark plugs using a wire gauge gap tool. |
| • | Visually and physically inspect secondary ignition for the following: |
| - | Ignition wires arcing to ground |
| - | Ignition wires for proper routing |
| - | Ignition coils for cracks or carbon tracking |
| • | Wet down the secondary ignition system with water from a spray
bottle. Wetting down the secondary ignition system may help locate damaged
or deteriorated components. Look and listen for arcing or misfiring
as you apply the water. |
|
Engine Cooling System
|
| • | Inspect the engine coolant level for being low. |
| • | Inspect the engine thermostat for proper operation and correct
heat range. |
|
Engine Mechanical
|
| • | Inspect engine mechanical for the following: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber-Leaking valve seals |
| • | For incorrect basic engine parts, inspect the following components: |
|
Additional Checks
|
| • | Visually and physically inspect the vacuum hoses for splits, kinks,
and proper connections and routing as shown on Vehicle Emission Control Information
label. Refer to
Emission Hose Routing Diagram
. |
| • | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
| • | Inspect the following exhaust system components for possible restrictions: |
| - | The exhaust system for physical damage |
| - | The exhaust manifold for a collapsed inner wall |
| - | The mufflers for heat distress or possible internal failure |
| - | The three-way catalytic converters (TWC) for possible plugged
pipes by comparing the exhaust system back pressure on each side of engine.
Check back pressure by removing HO2S near exhaust manifolds. |
| • | Electromagnetic interference (EMI) on the reference circuit can
cause an engine miss condition. A scan tool can usually detect EMI by monitoring
the engine RPM. A sudden increase in RPM with little change
in actual engine RPM change, may indicate that EMI is present.
If a problem exists, inspect for high voltage components near
ignition control circuits. |
| • | Inspect for faulty engine mounts. |
| • | Inspect the intake manifold and the exhaust manifold passages
for casting flash. |
|
