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 PCM wiring diagrams
|
| • | 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 Body and Accessories/Wiring Systems
for wiring repair procedures. |
|
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 Engine Electrical/Spark Plugs
. 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/Engine Mechanical
for diagnosis of the
oil fouling condition. |
| • | Check the spark plugs for proper heat range. Refer to Engine Electrical/Spark Plugs
. |
|
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/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 for an intermittent EGR problem. Refer to EGR System Diagnosis
. |
| • | Check the generator output voltage. |
|
