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
. |
| • | 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
|
| • | Inspect the heated oxygen sensors (HO2S). The HO2S should respond
quickly to different throttle positions. If they do not,
inspect 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 8.1L. |
| • | Inspect the mass air flow (MAF) sensor connections. Repair or
replace terminals. Refer to
Connector Repairs
in Wiring Systems. |
|
Fuel System
|
| • | Verify 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. |
| • | 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
Spark Plug Inspection
for diagnosis of 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
Electronic Ignition (EI) System Diagnosis
diagnosis table for diagnosis. |
|
Engine Mechanical
| Check engine mechanical for the following conditions:
| • | Sticking or leaking valves |
|
Additional Checks
| Inspect the vacuum hoses for splits, kinks, and proper
connections and routing as shown on Vehicle Emission Control Information
label.
|
