Checks
| Action
|
DEFINITION: Engine power variation under steady throttle
or cruise. Feels like the vehicle speeds up and slows down with
no change in the accelerator pedal.
|
Preliminary
|
| • | Search for service bulletins. |
| • | Be sure the driver understands the transmission torque converter
clutch (TCC), and the A/C compressor operation as explained in the owners
manual. Inform the customer how the TCC and the A/C clutch operates. |
| • | Inspect the PCM grounds for being clean, tight and in their proper
location. |
|
Sensor/System
|
| • | The O2S 1 and HO2S 2 should respond quickly to different
throttle positions. If not, inspect the O2S 1 and the HO2S 2
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 and HO2S 2
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 and the heated oxygen sensor
in the
Information Sensors/Switches Description
. |
| • | Test for proper operation of the following sensors: |
|
Fuel System
|
| • | Inspect the fuel filter for being plugged or restricted. |
| • | Ensure each injector harness is connected to the correct injector
and cylinder. |
| • | Inspect items which can cause an engine to run rich (Long Term
FT is significantly in the negative range). Refer to Diagnostic Aids for
DTC P0172 Fuel Trim System Rich
. |
| • | Inspect items that can cause an engine to run lean (Long Term
FT is significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171 Fuel Trim System Lean
. |
|
Ignition System
|
| • | Test for proper ignition voltage output with a J 26792
Spark Tester or equivalent. |
| • | Inspect the spark plugs for the following conditions: |
| - | Burnt 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. |
| • | Inspect the ignition control module (ICM) for proper ground connection. |
| • | Inspect the ignition coils for cracks or carbon tracking. |
| • | Test/inspect the spark plug wires for proper resistance and condition. |
|
Additional Checks
|
| • | Inspect the exhaust system for a possible restriction: |
| - | Inspect the exhaust system for damaged or for possible collapsed
pipes. |
| - | Inspect the muffler for heat distress or for possible internal
failure. |
| • | Inspect the vacuum lines for kinks or leaks. |
| • | Test 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 systems. |
|
