Lack of Power, Sluggish or Spongy
Checks
| Action
|
Definition: Engine delivers less than expected power. Little or no increase
in speed when the accelerator pedal is pushed down part way.
|
Preliminary Checks
|
| • | Refer to the Powertrain OBD System Check. |
| • | Refer to Important Preliminary Checks. |
| • | Refer to Visual/Physical Checks. |
|
Fuel System Checks
|
| • | Check the system fuel pressure. Refer to Fuel System Pressure
Test. |
| • | Check the fuel injectors. Refer to Fuel Injector Coil/Fuel Injector
Balance Test. |
| • | Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel
Testing. |
| • | Check items which can cause an engine to run rich (long term fuel
trim is significantly in the negative range). Refer to Diagnostic Aids for
DTC P0172. |
| • | Check items that can cause an engine to run lean (long term fuel
trim is significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171. |
|
Sensor/System
|
| • | Using a scan tool, monitor KS system for excessive spark retard
activity. Refer to Knock Sensor System. |
| • | Check the EGR system for proper operation. Refer to EGR System. |
| • | Check for a restricted air intake system. Refer to Air Induction
System. |
| • | Check for proper Boost Control System Operation (if equipped).
Refer to Boost Control System Check. |
|
Ignition System
|
| • | Check for proper ignition voltage output using the following steps: |
| - | Clip the spark tester J 26792 to engine ground. |
| - | Connect one end of a spark plug wire to the 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 spark tester; a crisp blue
spark should be observed. |
| - | Repeat the above steps for each coil. |
| • | If adequate spark is not present at the coil(s), check for the
following conditions: |
| - | Coil(s) - Cracks, carbon tracking/arcing, or a resistance value
outside the specified range. |
Coil Resistance
5000 - 8000 ohms (5K - 8K ohms) | - | Spark Plug wires - 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
7000 ohms (7K ohms)
| | 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 spark plugs and check 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. |
|
Engine Mechanical
|
| • | Excessive oil in combustion chamber-Leaking valve seals.
Refer to Engine Mechanical.
|
| • | Low cylinder compression. Refer to Engine Mechanical.
|
| • | For incorrect basic engine parts. Inspect the following: |
| • | Refer to Engine Mechanical.
|
|
Additional Checks
| Check exhaust system
for possible restrictions. Check for the following:
| • | Inspect exhaust system for damaged or collapsed pipes. |
| • | Inspect mufflers for heat distress or possible internal failure. |
| • | For possible plugged Three-Way catalytic converter. Refer
to Restricted Exhaust System Check and Exhaust System. |
| • | Check for proper TCC operation. Refer to Torque Converter Clutch
in Transaxle Diagnosis. |
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