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
|
| • | Monitor the heated oxygen sensors (HO2S). The HO2S 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 condition. |
| • | Monitor the 24 X 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 24 X and CMP sensor circuits for intermittents.
Refer to
Testing for Intermittent Conditions and Poor Connections
in Wiring Systems. |
| • | Monitor the 3 X parameter on the scan tool. If the 3 X
is not responding, inspect the 7 X CKP sensor and circuits for intermittents.
Inspect the ignition control (IC) circuit, bypass circuit, 3 X reference
high circuit, and the 3 X reference low circuit for intermittents.
If these circuits become open or shorted, the conditions 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. |
|
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
DTC P0172
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
DTC P0171
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
. 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
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
1 968 ohms per meter (600 ohms per foot).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent condition. 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 the 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
. |
|
