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
|
| • | Inspect 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 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 powertrain control module (PCM) will reduce
the amount of fuel delivered to the engine, causing a severe driveability
problem. |
| • | Inspect for proper operation of the manifold absolute pressure
(MAP) sensor. |
| • | Inspect for proper operation of the throttle position (TP) sensor. |
| • | Inspect for proper operation of the engine coolant temperature
(ECT) sensor. |
|
Fuel System
|
| • | Inspect items which can cause an engine to run rich--the
Short term FT is significantly in the negative range. Refer to Diagnostic
Aids for
DTC P0172
. |
| • | Inspect items that can cause an engine to run lean--Short
term FT is significantly in the positive range. Refer to Diagnostic Aids
for
DTC P0171
. |
| • | Inspect for proper operation of the evaporative emission (EVAP)
control system. |
|
Ignition System
|
| • | Inspect for proper ignition voltage output with a J 26792
Spark Tester or equivalent. |
| • | Inspect 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 |
| • | Using the scan tool and monitoring the cylinder misfire screen
can aid in pinpointing a specific cylinder fault. |
| • | If the spark plugs are fuel or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
| • | Inspect the ignition control module (ICM) for proper ground connection. |
| • | Inspect the ignition coils for cracks or carbon tracking. |
| • | Inspect the spark plug wires for proper resistance and condition. |
|
Additional Checks
|
| • | Inspect for proper operation of the automatic transmission. |
| • | Inspect 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: |
| - | All electrical connections within the suspected circuit and/or
systems |
| - | If the short term FT is attempting to lean an engine with a rich
condition, the negative fuel trim numbers are above 20, hesitation on tip
in throttle is usually the result. |
|
