Checks
| Action
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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.
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Preliminary
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| • | Be sure driver understands transmission torque converter clutch,
and A/C compressor operation as explained in the owners manual. Inform customer
how TCC and the A/C clutch operates. |
|
Sensor/System
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| • | Inspect the heated oxygen sensors. The Heated Oxygen sensors should
respond quickly to different throttle positions. If not, inspect the HO2S
for silicon or other contaminants from fuel or use of improper
RTV sealant. The sensors may have a white powdery coating.
Silicon contamination causes a high but false HO2S signal
voltage (rich exhaust indication). Refer to
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate
RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption.
Remove the HO2S and visually inspect the portion of the sensor exposed to
the exhaust stream in order to check for contamination. If contaminated, the
portion of the sensor exposed to the exhaust stream will have a white powdery
coating. Silicon contamination causes a high but false HO2S signal voltage
(rich exhaust indication). The control module will then reduce the amount
of fuel delivered to the engine, causing a severe driveability problem. Eliminate
the source of contamination before replacing the oxygen sensor.
. The PCM
will reduce the amount of fuel delivered to the engine, causing
a severe driveability problem. Refer to
Information Sensors/Switches Description
. |
| • | Inspect the MAF sensor and related wiring. |
|
Fuel System
|
| • | Ensure each injector harness is connected to the correct injector/cylinder. |
| • | Inspect items which can cause an engine to run rich (long term
fuel trim is significantly in the negative range). Refer to Diagnostic Aids
in
DTC P0172 Fuel Trim System Rich
. |
| • | Inspect items that can cause an engine to run lean (long term
fuel trim is significantly in the positive range). Refer to Diagnostic Aids
in
DTC P0171 Fuel Trim System Lean
. |
|
Ignition System
|
| • | Inspect for proper ignition voltage output using the following
steps: |
| - | Clip the J 26792
spark tester to engine ground. |
| - | Connect one end of a spark plug wire to the J 26792
spark tester. Leave the other end of
the spark plug wire to the coil being tested. |
| - | Connect one end of another spark plug wire to the other coil
tower. Connect the other end of the spark plug wire to ground. |
| - | Crank the engine while observing the J 26792
spark tester. A spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If spark is not present at the plugs, inspect for the following
conditions: |
| - | Inspect the coils for cracks, carbon tracking/arcing or a resistance
value outside the specified range. |
Coil Resistance
5K-7K ohms (5,000-7,000 ohms) | - | Inspect the spark plug wires for signs of arcing/cross firing,
cracks, carbon tracking, plug boot damage, pinched, improper routing or a
resistance value outside the specified range. |
Spark Plug Wire Resistance
1 968 ohms per meter ( 600 ohms per foot).
| | Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components will arc to ground
when a secondary component is faulty.
|
| - | Ignition System Wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove the spark plugs and inspect for the following: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
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Additional Checks
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| • | Inspect the exhaust system for possible restriction: |
| - | Inspect the exhaust system for damaged or collapsed pipes. |
| - | Inspect the muffler for heat distress or possible internal failure. |
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