Checks
| Actions
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DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust system, making loud
popping noise.
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Preliminary Checks
|
| • | Refer to
Symptoms
for Important
Preliminary Checks Before Starting. |
| • | Inspect the PCM grounds for being clean, tight and in their proper
locations. |
|
Fuel System
|
| • | Inspect for restricted fuel filter. |
| • | Inspect each injector harness is connected to the correct injector/cylinder
according to the firing order. Relocate injector harnesses as necessary. |
|
Sensor/System
|
| • | Inspect EGR for being loose or for a faulty gasket. |
| • | Inspect EGR operation for being open all the time. |
| • | Inspect intake air system and crankcase for air leaks. |
| • | Inspect crankcase ventilation valve for proper operation. Place
finger over inlet hole in valve end several times. If the valve does not snap
back, the valve needs to be replaced. Refer to
Exhaust Gas Recirculation Valve Replacement
. |
| • | Inspect for proper calibration of speedometer. Connect J 33431-C
to VSS electrical connector. Ignition
ON, tester ON and monitor the speedometer. The speedometer should indicate
the speed being generated. |
| • | Using a Scan Tool, monitor TP sensor voltage. The TP sensor voltage
should be less then 0.9 volts at rest. If the TP sensor voltage is greater
than 0.9 volt, inspect the throttle body and accelerator cables
for binding. |
| • | Using a scan tool, monitor KS system for excessive spark retard
activity. |
|
Ignition System
|
| • | Using the scan tools snapshot feature may help locate an intermittent
ignition failure. Abnormal signals can cause a backfire on acceleration. Inspect
for an intermittent ignition system malfunction in the following circuits: |
| - | Intermittent 4X circuit |
| - | Intermittent 24X circuit |
| - | Intermittent Ignition Control circuit |
| • | Remove the spark plugs and Inspect for the following conditions: |
| • | An improper spark plug gap will cause a driveability problem.
Measure and adjust the gap of the spark plugs. Refer to
Spark Plug Usage
in Engine Electrical. |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. Refer to
Spark Plug Visual Diagnosis
in Engine Electrical. |
| • | Replace spark plugs that cannot be cleaned and re-used. Refer
to
Spark Plug Replacement
in Engine
Electrical. |
| • | Visually/Physically inspect secondary ignition for the following
conditions: |
| - | Ignition wires for cross firing |
| - | 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 to locate damaged or deteriorated components. Look/listen for arcing
or misfiring as water is applied. |
| • | Inspect for loose ignition control module ground. |
|
Engine Cooling System
|
| • | Inspect engine coolant level for being low. Refer to
Loss of Coolant
in Engine Cooling. |
| • | Inspect engine thermostat for proper operation or for wrong heat
range. Refer to
Thermostat Diagnosis
in Engine Cooling. |
|
Engine Mechanical
|
| • | Inspect engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber-leaking valve seals |
| - | Low cylinder compression |
| • | Test engine compression. Refer to Engine Compression
Test
in Engine Mechanical. |
| • | Inspect the following components for incorrect basic engine parts: |
|
Additional Checks
|
| • | Visually (physically) inspect for the following conditions: |
| - | Splits in the vacuum hoses |
| - | Kinks in the vacuum hoses |
| - | Proper connections as shown on Vehicle Emission Control Information
label. |
| - | Proper routing as shown on Vehicle Emission Control Information
label |
| • | Verify TCC operation. The scan tool should indicate an RPM drop
when the TCC is commanded ON. Refer to
Torque Converter Diagnosis
in Automatic Transaxle--4T80-E. |
| • | Inspect exhaust system for possible restriction. Perform the following
procedures: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
| - | Inspect the exhaust system back pressure on each side of engine. |
| • | An engine miss condition can be caused by electromagnetic interference
(EMI) on the reference circuit. EMI can usually be detected by monitoring
engine RPM with a scan tool. A sudden increase in RPM with little change
in actual engine RPM change, indicates EMI is present. If a problem
exists, inspect the routing of secondary ignition wires, high voltage
components, located near the ignition control circuits. |
| • | Inspect PNP switch circuit and be sure the scan tool indicates
vehicle is in drive with gear selector in drive or overdrive. |
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