Checks
| Actions
|
DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust system, making loud
popping noise.
|
Preliminary Checks
|
| • | Search for any bulletins. |
| • | Verify that the PCM grounds are clean, tight, and in the correct
locations. |
|
Fuel
System
|
| • | Inspect for a restricted fuel filter. |
| • | Verify that each fuel injector harness is connected to the correct
injector and cylinder according to the firing order. Relocate any fuel injector
harnesses as necessary. |
|
Sensor
and System
|
| • | Inspect the exhaust gas recirculation (EGR) valve for being loose
and for a faulty gasket. Inspect the EGR valve for being open all the time. |
| • | Inspect the air intake system and the crankcase for air leaks. |
| • | Inspect the crankcase ventilation valve for correct operation.
Place a finger over the inlet hole in the valve end several times. The valve
should snap back. If not, replace valve. |
| • | Inspect for the correct speedometer calibration. Connect the J 33431-C
Signal Generator to
the vehicle speed sensor (VSS) electrical connector. With the ignition on
and the tester on, monitor the speedometer. The speedometer should indicate
the speed being generated. |
| • | Using a scan tool, monitor the throttle position (TP) sensor voltage.
The TP sensor voltage should be less than 0.9 volt at rest. If the
TP sensor voltage is more than 0.9 volt, inspect the throttle body
and the accelerator cables for binding. |
| • | Using a scan tool, monitor the knock sensor (KS) system for any
excessive spark retard activity. |
|
Ignition
System
| Remove
the spark plugs. Inspect for the following:
| | An improper spark plug gap will cause a driveability problem. The spark
plug gapping should be done with a wire gage gap tool . |
If the spark plugs are gas or oil fouled, determine the cause of the
fouling before replacing the spark plugs.
Inspect the plugs and the coils for signs of arcing, cracks, or carbon
tracking.
| • | Inspect for any loose ignition control module (ICM) grounds. |
| • | Inspect the spark plugs for the correct heat range. |
|
Engine
Cooling System
|
| • | Inspect for a low engine coolant level. |
|
Engine
Mechanical
| Inspect for the following conditions:
| • | Any excessive oil in the combustion chambers may indicate leaking
valve seals. Refer to
Oil Consumption Diagnosis
in Engine Mechanical-3.5L. |
| • | Any incorrect basic engine parts. Inspect the following: |
Refer to
Symptoms - Engine Mechanical
in
Engine Mechanical-3.5L.
|
Additional Checks
|
| • | Inspect the vacuum hoses for splits, kinks, and the correct connections
and routing as shown on the Vehicle Emission Control Information label. |
| • | Inspect the exhaust system for a restriction. Refer to
Restricted Exhaust
in Engine Exhaust. |
| • | Inspect for any improper harness routing. An engine miss condition
can be caused by electromagnetic interference (EMI) on some engine controls
circuits. Use the scan tool to inspect for any erratic sensor values
or excessive changes in the indicated RPM with little change in the
actual engine RPM. This may indicate EMI is present. If a problem exists,
inspect for an improper routing of the harness near high voltage components
or the high current components. |
| • | Inspect the charging system. A bad diode in the alternator can
allow A/C noise to enter the electrical system. This may affect the engine
controls system operation. Refer to
Diagnostic Starting Point - Engine Electrical
in Engine Electrical. |
| • | Inspect the transaxle range (TR) switch circuit. Ensure that the
scan tool indicates the vehicle is in drive with the gear selector in Drive
or in Overdrive. |
|
