Inspection/Test
| Action
|
DEFINITION: Steady pulsation or jerking that follows engine speed, usually
more pronounced as engine load increases.
|
Preliminary
|
|
Fuel System
|
| • | Inspect any items which may cause an engine to run rich, long term fuel
trim is significantly in the negative range. Refer to Diagnostic Aids for
DTC P0172
. |
| • | Inspect any items which may cause an engine to run lean, long term fuel
trim is significantly in the positive range. Refer to Diagnostic Aids for
DTC P0171
. |
|
Sensor/System
|
| • | Inspect for conditions which cause an incorrect idle speed: |
| - | Restricted air intake system |
| - | Inspect the air intake ducts for being collapsed, damaged areas, looseness,
improper installation, or leaking especially between the mass air flow (MAF) sensor
and the throttle body. |
| • | Inspect the throttle position (TP) sensor and related circuit wiring.
Refer to
DTC P0123
. |
| • | Monitor the 24X crank sensor and the CMP sensor signal parameters on
the scan tool. If both are not responding, test the sensor feed circuit. Both sensors
use a separate feed circuit but are internally connected to power. Test all CKP
sensor A and CMP sensor circuits for intermittents. Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring
Systems. |
| • | Monitor the 3X crank sensor parameter on the scan tool. If the 3X crank
sensor parameter is not responding, inspect the CKP sensor B and circuits
for intermittents. Inspect the ignition control (IC) circuit, IC timing control
circuit, low resolution engine speed signal circuit and the low reference circuit
for intermittents. If these circuits become open, or shorted, they may not set
a diagnostic trouble code (DTC) immediately, but are capable of causing driveability
complaints. Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Test the positive crankcase ventilation (PCV) valve for proper operation. |
| • | Inspect the Transaxle Range Switch input with the vehicle in drive and
the gear selector in drive or overdrive. |
| • | Inspect the following for damage: |
| • | Bent balancer interrupter rings |
| • | Damaged crankshaft position sensor |
|
Ignition System
|
| • | Inspect for proper ignition voltage output using the following steps: |
| 1. | Attach the J 26792
Spark
Tester to engine ground. |
| 2. | Connect the spark plug end of the spark plug wire to the J 26792
. Leave the other end of the spark plug wire
connected to the coil being tested. |
| 3. | Connect the spark plug end of the companion spark plug wire to ground.
The companion spark plug wire is the wire attached to the corresponding coil tower. |
| 4. | Crank the engine while observing the J 26792
. A spark should be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If spark is not present at the coils, inspect for the following conditions: |
| - | Coils--Cracks, carbon tracking/arcing, or a resistance value outside
the specified range |
Coil Resistance
5000-8000 ohms (5K-8K ohms) | - | Spark plug wires--Signs of arcing, cross firing, cracks, carbon
tracking, plug boot damage, pinched, improper routing, or a resistance
value outside the specified range |
Spark Plug Wire Resistance
9 686 ohms per meter (3,000 ohms per foot)
| | Important: : Spraying the secondary ignition wires with a light mist of water may help locate
an intermittent problem. Ignition voltage will arc to ground when a secondary component
is faulty.
|
| - | Defective ignition module |
| - | Ignition system wiring--Loose ignition module feed or ground connection,
or damaged system wiring |
| • | Remove spark plugs and inspect for the following conditions: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | 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 Inspection
. |
|
Engine Mechanical
|
| • | Inspect engine mechanical for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber--Leaking valve seals |
| - | Low cylinder compression |
| • | For incorrect basic engine parts--Inspect the following components: |
|
Additional
|
| • | Inspect the exhaust system for possible restrictions: |
| - | Inspect exhaust system for damaged or collapsed pipes. |
| - | Inspect mufflers for heat distress or possible internal failure. |
| - | For possible plugged catalytic converter |
| • | 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 routing of secondary ignition wires, high voltage components, near the
ignition control circuits. |
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