Inspection/Test
| Action
|
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.
|
Preliminary
|
|
Sensor/System
|
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 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 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 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 the following conditions: |
| - | Leaking conditions especially between the MAF sensor and
the throttle body |
|
Fuel System
|
| • | Test for faulty fuel injectors. Refer to the following test 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
. |
|
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. |
| | 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.
|
| • | If spark is not present at the coils, inspect the following components
for the specified conditions: |
| - | Coils--Cracks, carbon tracking and/or arcing, or a resistance
value outside the specified range |
Coil Resistance
5000-8000 ohms (5K-8K ohms)
Spark Plug Wire Resistance
9868 ohms per meter (3000 ohms per foot)
| • | A resistance value outside the specified range |
| - | Defective ignition module |
| - | Ignition system wiring for loose ignition module feed or ground
connection, or damaged system wiring |
| • | Remove the 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
in Engine Electrical. |
|
