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
torque converter clutch 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 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
. |
| • | 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: 1-8-7-2-6-5-4-3).
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
DTC P0172 Fuel Trim System Rich Bank 1
and
DTC P0175 Fuel Trim System Rich Bank 2
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 the TCC operation. A TCC applying too soon can cause the
engine to spark knock. Refer to Transmission/Transaxle/Automatic
Transmission
. |
|
