Inspection/Test
| Action
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DEFINITION: Momentary
lack of response as the accelerator is pushed down. Can occur at any vehicle
speed. Usually more pronounced when first trying to make
the vehicle move, as from a stop sign. May cause the engine
to stall if severe enough.
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Preliminary
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Sensor/System
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| • | Monitor the heated oxygen sensors (HO2S). The heated oxygen sensors
should respond quickly to different throttle positions. If not, inspect the
HO2S for silicon or other contaminants from fuel or use of
improper RTV sealant. The sensors may have a white powdery
coating. Silicon contamination causes a high but false HO2S
signal voltage, rich exhaust indication. Refer to
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate
RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption.
Remove the HO2S and visually inspect the portion of the sensor exposed to
the exhaust stream in order to check for contamination. If contaminated, the
portion of the sensor exposed to the exhaust stream will have a white powdery
coating. Silicon contamination causes a high but false HO2S signal voltage
(rich exhaust indication). The control module will then reduce the amount
of fuel delivered to the engine, causing a severe driveability problem. Eliminate
the source of contamination before replacing the oxygen sensor.
. The PCM will reduce the amount of fuel delivered to
the engine, causing a severe driveability problem. |
| • | Monitor the 24X crankshaft position (CKP) and camshaft position
(CMP) sensors on 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 24X and CMP sensor circuits for intermittents. Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Monitor the 3X parameter on the scan tool. If the 3X is not responding,
inspect the 7X CKP sensor and circuits for intermittents. Inspect the ignition
control (IC) circuit, bypass circuit, 3X reference high circuit, and the
3X reference low circuit for intermittents. If these circuits become open,
or shorted they 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. |
| • | Inspect the throttle position (TP) sensor and related wiring. |
| • | Inspect the mass air flow (MAF) sensor and related wiring. Inspect
the air intake ducts for being collapsed, damaged areas, looseness, improper
installation, or leaking especially between the MAF sensor and the throttle
body. |
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Fuel System
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| • | Test the injectors. Refer to the following procedures: |
| • | 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. |
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Ignition System
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| • | 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
spark tester; 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
spark tester; 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
5000-8000ohms (5K-8Kohms) | - | 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
600ohms per foot (1 968ohms per meter).
| | 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.
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| - | 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. |
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