Checks
| Actions
|
DEFINITION:
Fuel ignites in the intake manifold or in the exhaust system, making a loud
popping noise.
|
Preliminary Checks
|
| • | Check the PCM grounds for being clean, tight and in their proper
locations. Refer to
Wiring Repairs
in Wiring Systems. |
|
Fuel
System
|
| • | Check that each injector harness is connected to the correct injector/cylinder
according to the firing order (firing order: 1-8-4-3-6-5-7-2).
Relocate injector harnesses as necessary. |
|
Sensor/System
|
| • | Check the Air intake system and crankcase for air leaks. |
| • | Check 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. |
| • | Check for proper calibration of speedometer. |
Use a scan tool in order to monitor the KS system for excessive spark
retard activity. Refer to
Knock Sensor (KS) System Description
.
|
Ignition System
|
| • | Check for proper ignition voltage output with spark tester J 26792
. |
| • | Check for an intermittent ignition system malfunction in the following
circuits: |
| - | Intermittent ignition control circuit. |
| - | Use the scan tool's Snapshot feature in order to help locate an
intermittent ignition failure. |
| • | Remove spark plugs and check for the following: |
| • | An improper spark plug gap will cause a driveability problem.
Do the spark plug gapping using a wire gauge gap tool (J 41319).
Determine the cause of the fouling before replacing the spark plugs
if the spark plugs are gas or oil fouled. Refer to
Fuel System Diagnosis
for diagnosis of the rich condition
or for diagnosis of the oil fouling condition. |
| • | Visually/Physically inspect secondary ignition for the following: |
| - | Ignition wires for cross firing |
| - | Ignition wires arcing to ground |
| - | Ignition coils arcing to ground |
| • | 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/listen for arcing or misfiring as
you apply the water. |
|
Engine
Cooling System
|
| • | Check the engine coolant level for being low. |
| • | Check the engine thermostat for proper operation or for the wrong
heat range. |
|
Engine
Mechanical
|
| • | Check engine mechanical for the following: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber-Leaking valve seals |
| - | Low cylinder compression |
| • | For incorrect basic engine parts. Inspect the following: |
| • | Refer to Engine Mechanical for diagnosis procedures. |
|
Additional
Checks
|
| • | Visually (physically) check the vacuum hoses for splits, kinks,
and proper connections and routing as shown on Vehicle Emission Control Information
label. |
| • | Check the intake manifold and the exhaust manifold passages for
casting flash. |
| • | Check the EGR gasket for a faulty or loose fit. |
| • | Check the exhaust system for possible restrictions. Check the
following: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the exhaust manifold for a collapsed inner wall. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Inspect for possible plugged catalytic converters by comparing
exhaust system back pressure on each side of engine. Check back pressure by
removing front Heated Oxygen Sensor (HO2S) near exhaust manifolds. Refer
to
Restricted Exhaust System Check
. |
| • | 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,
check the routing of the secondary ignition wires or high voltage components
near ignition control circuits. |
| • | Check for faulty motor mounts. |
| • | Check the intake manifold and the exhaust manifold passages for
casting flash. |
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