Hesitation, Sag, Stumble
Checks
| Action
|
DEFINITION: A momentary lack of
response as the accelerator is pushed down. Hesitation, sag, or stumble can
occur at any vehicle speed. It is usually more pronounced when
the driver first attempts to make the vehicle move, for example,
starting up after being stopped at a stop sign. Hesitation, sag, or stumble
can cause the engine to stall if the symptoms are severe enough.
|
Preliminary
|
| • | Search for service bulletins. |
|
Sensor/System
|
| • | Check the oxygen sensor (O2S 1). The O2S 1 should
respond quickly to different throttle positions. If not, check the O2S 1
for silicon or other contaminants from fuel or from the use of
an improper room-temperature vulcanizing (RTV) sealant. The sensors
may have a white powdery coating indicative of silicon contamination,
which may cause a high but false O2S 1 signal voltage,
indicating a rich exhaust. The PCM will reduce the amount of fuel
that is delivered to the engine, causing a severe driveability problem.
|
| • | Check for proper operation of: |
| - | The manifold absolute pressure (MAP) sensor |
| - | The throttle position (TP) sensor |
| - | The engine coolant temperature (ECT) sensor |
|
Fuel System
|
| • | Check the items which can cause an engine to run rich, where long-term
fuel trim is significantly in the negative range. Refer to Diagnostic Aids
for
DTC P0172
. |
| • | Check items that can cause an engine to run lean, where long-term
fuel trim is significantly in the positive range. Refer to Diagnostic Aids
for
DTC P0171
. |
| • | Check for proper operation of the evaporative emission (EVAP)
control system. |
|
Ignition System
|
| • | Check for proper ignition voltage output with the J 26792
Spark Tester or equivalent. |
| • | Check the spark plugs for the following conditions: |
| - | Wet or fuel fouled spark plugs |
| - | Cracks on the spark plugs |
| - | Improper spark plug gap |
| - | Burned electrodes or heavy deposits |
| • | If the spark plugs are fuel or oil-fouled, determine the cause
of the fouling before replacing the spark plugs. |
| • | Check the ignition control module (ICM) for proper ground connection. |
| • | Check the ignition coils for cracks or carbon tracking. |
| • | Check the spark plug wires for proper resistance and condition. |
|
Additional Checks
|
| • | Check for proper operation of the automatic transaxle. Refer to
Road Test
in Automatic Transaxle-4T40,
or
Road Test
in Automatic Transaxle-3T40. |
| • | Check the generator output voltage. Repair the generator if the
output voltage is less than 11 volts or more than 16 volts. |
| • | If all procedures have been completed and no malfunctions have
been found, review and inspect the following items: |
| - | Inspect all electrical connections within the suspected circuit
and/or systems. |
|
