Hesitation, Sag, Stumble
Checks
| 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
|
| • | Search for service bulletins. |
|
Sensor/System
|
| • | Check the Oxygen sensor (O2S 1). The O2S 1should respond quickly
to different throttle positions. If not, check the O2S 1 for silicon or other
contaminants from fuel or the use of improper RTV sealant. The sensors
may have a white powdery coating. Silicon contamination causes a high but
false O2S 1 signal voltage (rich exhaust indication). The PCM will reduce
the amount of fuel delivered to the engine, causing a severe driveability
problem. Refer to Oxygen sensor in
Information Sensors/Switches Description
. |
| • | Check for proper operation of the MAP Sensor. |
| • | Check for proper operation of the TP sensor. |
| • | Check for proper operation of the ECT sensor. |
|
Fuel
System
|
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis
. |
| • | Check items which can cause an engine to run rich (long term fuel
trim is significantly in the negative range). Refer to Diagnostic Aids for
DTC P0172 Fuel Trim System Rich
. |
| • | Check items that can cause an engine to run lean (long term fuel
trim is significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171 Fuel Trim System Lean
. |
| • | 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: |
| - | Check for wet or fuel fouled spark plugs. |
| - | Check for cracks on the spark plugs. |
| - | Check for improper spark plug gap. |
| - | Check for burned electrodes or heavy deposits. |
| • | If the spark plugs are fuel or oil fouled, the cause of the fouling
must be determined 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 Transmission. |
| • | 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
not been found, review and inspect the following items: |
| - | Visually and physically inspect all electrical connections within
the suspected circuit and/or systems. |
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