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 may 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 present 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 may not set a 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
. Connect the other end of the spark plug
wire 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
5,000-8,000 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
9,868 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 condition. Ignition
voltage arcs 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 |
| • | Inspect for incorrect engine parts, such as following basic components: |
|
Additional
|
| • | Inspect the exhaust system for possible restrictions: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the mufflers for heat distress or possible internal failure. |
| - | Test for possible catalytic converter restrictions by testing the exhaust
system back pressure. |
| • | 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 speed indicates EMI is present. If a
condition exists, inspect the routing of secondary ignition wires,
or high voltage components near the ignition control circuits. |
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