Checks
| Action
|
DEFINITION: Engine
delivers less than expected power. An absence of, or minor increases in speed
when the accelerator pedal is pushed down part-way.
|
Preliminary Checks
|
|
Fuel System
|
| • | Test the following items: |
| • | Test items which can cause an engine to run rich, with the long-term
fuel trim (FT) significantly in the negative range. Refer to Diagnostic Aids
for
DTC P0172 or P0175
. |
| • | Test items that can cause an engine to run lean, with the long-term
FT significantly in the positive range. Refer to Diagnostic Aids for
DTC P0171 or P0174
. |
|
Sensor/System
|
| | If knock retard is above 10-12 degrees, disconnect the
KS and ground the sensor harness connector. Monitor the knock retard on the
scan tool. A knock retard should not be present. If a knock retard is
still present, the powertrain control module (PCM) is malfunctioning.
Replace the PCM. Refer to
Powertrain Control Module Replacement
. |
|
Ignition System
|
| • | Test for proper ignition voltage output using the following steps: |
| 1. | Clip the J 26792
Spark Tester to engine ground. |
| 2. | Connect one end of a spark plug wire to the spark tester. Connect
the other end of the spark plug wire to the coil being tested. |
| 3. | Connect another spark plug wire between the remaining tower of
the coil being tested and ground. |
| 4. | Crank the engine while observing the spark tester, a spark should
be observed. |
| 5. | Repeat the above steps for each coil. |
| • | If adequate spark is not present at the coils, test for the following
conditions: |
| - | Coils--Evidence of carbon tracking or arcing, cracks in the
coils, or a resistance value outside the specified range: |
Coil Secondary Resistance
5000-8000 ohms (5K-8K ohms)
| | Important: Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent condition. Ignition components will arc to ground
when a secondary component is malfunctioning.
|
| - | Spark plug wires--Inspect for the following conditions: |
| • | Evidence of cross firing |
| - | Spark plug wires--Inspect for a resistance value more than
the specified value: |
Spark Plug Wires Resistance
3280-4921 ohms/meter (1000-1500 ohms/ft) | - | Malfunctioning ignition control module |
| - | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and inspect for the following conditions: |
| - | Burned or damaged electrodes |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
|
Engine
Mechanical
|
| • | Inspect for the following conditions: |
| - | Excess oil in combustion chamber-Inspect for leaking valve
seals. |
| - | Low cylinder compression |
| • | Inspect for incorrect engine parts, such as the following basic
parts: |
|
Additional
Tests
|
| • | Inspect the exhaust system for a possible restriction in the following
components: |
| - | Damaged or collapsed pipes |
| - | Heat distress or possible internal failure in the muffler |
| - | Plugged three-way catalytic converter--Test for possible
plugged conditions. Refer to
Restricted Exhaust
in Engine Exhaust. |
|
