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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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.
| • | 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. The powertrain control module (PCM) will reduce
the amount of fuel delivered to the engine, causing a severe driveability problem. |
| • | Monitor the 24X crank sensor and the camshaft position (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 crankshaft position (CKP) 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 3X 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. |
| • | 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. |
| • | Test the exhaust gas recirculation (EGR) system for proper operation,
if applicable. |
| • | Test the TP sensor and related wiring. |
| • | Test the MAF sensor and related wiring. |
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Fuel System
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| • | 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
. 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.
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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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