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 position.
|
Preliminary
|
| • | Be sure the driver understands the operation of the transmission torque
converter clutch (TCC) and A/C compressor operation as explained in the owners
manual. Inform the customer how the TCC and the A/C clutch operates. |
|
Sensor/System
|
| • | Check the heated oxygen sensors (HO2S). The HO2S should respond quickly
to different throttle positions. If they do not, check the HO2S
for silicon or other contaminates from fuel or the use of improper
RTV sealant. The sensors may have a white , powdery coating and result
in a high but false signal voltage rich exhaust indication. The
powertrain control module (PCM) will then reduce the amount of fuel
delivered to the engine causing a severe driveability problem.
For more information, refer to
Oil Consumption Diagnosis
in Engine Mechanical 8.1L. |
| • | Check the MAF sensor connections. Repair or replace terminals. Refer
to
Connector Repairs
in Wiring
Systems. |
|
Fuel System
|
| • | Check that each injector harness is connected to the correct injector
or cylinder according to the firing order firing order: 1-8-7-2-6-5-4-3.
Relocate injector harnesses as necessary. |
| • | Check the items that cause an engine to run rich long term fuel trim
near -13 percent. For a rich condition, refer to
DTC P0172 or P0175
. |
| • | Check the items that can cause an engine to run lean long term fuel
trim near 24 percent. For a lean condition, refer to
DTC P0171 or P0174
. |
|
Ignition System
|
| • | Wet down the secondary ignition system with water from a spray bottle.
Wetting down the secondary ignition system may help locate damaged
or deteriorated components. Look and listen for arcing or misfiring
as you apply the water. |
| • | Remove the spark plugs and check for the following: |
| • | An improper spark plug gap will cause a driveability problem. Gap the
spark plugs using a wire gauge gap tool. Refer to
Spark Plug Replacement
. |
| • | Determine the cause of the fouling before replacing the spark plugs
if the spark plugs are gas, coolant, or oil fouled. Refer to one of the following
procedures: |
| • | Monitor the Misfire Current Counters while driving the vehicle in the
conditions that the misfire occurred. If a cylinder can be located with a misfire,
use the DTC P0300 table for diagnosis. |
|
Engine Mechanical
| Ensure that the engine coolant temperature is not above 130°C (266°F).
This condition causes the PCM to operate in Engine Coolant Over
Temperature-Fuel Disabled Mode. While in Engine Coolant Over
Temperature-Fuel Disabled Mode, the PCM turns fuel OFF to four
cylinders at a time to keep engine temperatures from reaching
damaging levels. The system perceives Engine Coolant Over Temperature-Fuel
Disabled Mode as a lack of power, miss, or rough idle. If the
vehicle operates in Engine Coolant Over Temperature-Fuel Disabled
Mode, refer to
Engine Overheating
in Engine Cooling for diagnosis.
|
Additional Checks
|
| • | Visually (physically) check vacuum hoses for splits, kinks, and proper
connections and routing as shown on Vehicle Emission Control Information
label. |
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