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
|
| • | Refer to
Symptoms
,
Important Preliminary Checks Before Starting. |
| • | Check the PCM grounds for being clean, tight and in their proper
locations. Refer to
Wiring Repairs
in Wiring Systems. |
| • | Be sure the driver understands the operation of the transmission
and A/C compressor operation as explained in the owners manual. |
|
Sensor/System
|
| • | Check the Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensors
(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
Information Sensors/Switches Description
. |
| • | Check the MAF sensor connections. Repair or replace terminals.
Refer to
Wiring Repairs
in Wiring
Systems. |
|
Fuel
System
|
| • | Check that each injector harness is connected to the correct injector/cylinder
according to the firing order (firing order: 1-8-4-3-6-5-7-2).
Relocate injector harnesses as necessary. |
|
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/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.
Refer to
Maintenance Items
in Maintenance and
Lubrication. Do the spark plug gapping using a wire gauge gap tool (J 41319).
Refer to Spark Plug Replacement. Determine the cause of the fouling
before replacing the spark plugs if spark plugs are gas or oil fouled.
Refer to
Fuel System Diagnosis
for
diagnosis of the rich condition or Engine Mechanical for diagnosis
of the oil fouling condition. |
| • | Check the spark plugs for proper heat range. Refer to
Maintenance Items
in Maintenance and Lubrication. |
|
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
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. |
| • | Check the generator output voltage. |
|
