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
|
| • | Inspect the powertrain control module (PCM) grounds for being
clean, tight, and in the proper locations. Refer to
Engine Controls Schematics
. |
| • | Verify 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
|
| • | Inspect 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 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. |
| • | Inspect the mass air flow (MAF) sensor connections. Repair or
replace terminals. Refer to
Connector Repairs
in Wiring Systems. |
|
Fuel System
|
| • | Inspect 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. |
| • | Inspect the items that cause an engine to run rich long term fuel
trim near-13 percent. For a rich condition, refer to
DTC P0132 or P0152
. |
| • | Inspect the items that can cause an engine to run lean long term
fuel trim near 24 percent. For a lean condition, refer to
DTC P0131 or P0151
. |
|
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: |
Refer to
Spark Plug Inspection
.
| • | 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
DTC P0172 or P0175
for diagnosis of the rich
condition. Refer to
Spark Plug Inspection
for diagnosis of coolant or oil fouled spark plugs. |
| • | 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
| Verify that the engine coolant temperature (ECT) 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 and physically inspect vacuum hoses for splits, kinks,
and proper connections and routing as shown on Vehicle Emission Control
Information label. |
|
