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 and the A/C compressor operation as explained in the owners manual.
Inform the customer how the TCC and the A/C clutch operates. |
| • | Check the PCM grounds for being clean, tight and in their proper
location. |
|
Sensor/System
|
| • | Check the oxygen sensor (O2S 1) and the heated oxygen sensor (HO2S
2). The O2S 1 and HO2S 2 should respond quickly to different throttle positions.
If not, check 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. |
| • | 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 the fuel filter for being plugged or restricted. |
| • | Ensure each injector harness is connected to the correct injector/cylinder.
Refer to the Engine Controls Wiring Diagrams. |
| • | Check 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
. |
| • | Check 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
. |
|
Ignition System
|
| • | Check for proper ignition voltage output with spark tester J 26792
. |
| • | Check the spark plugs for the following conditions: |
| - | Improper spark plug gap |
| - | 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 torque converter clutch (TCC).
Refer to Automatic Transmission Diagnosis. |
| • | Check 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. |
| - | Check for possible plugged three-way catalytic converter. Refer
to Restricted Exhaust System Check
or diagnostic
procedures in Exhaust System. |
| • | Check the vacuum lines for kinks or leaks. |
| • | 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: |
| - | All electrical connections within the suspected circuit and/or
systems |
|
