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
|
|
Fuel System Checks
|
| • | 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 (KS) System Description
. |
| • | Check the EGR system for proper operation. Refer to EGR System Description
. |
| • | Check for a restricted air intake system. |
|
Ignition System
|
| • | Check 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 coil(s), check for the following
conditions: |
| - | Coil(s)--Cracks, carbon tracking/arcing, or a resistance
value outside the specified range. |
Coil Resistance
5000-8000ohms (5K-8Kohms) | - | 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
600ohms per foot (1 968ohms per meter).
| | 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 Oil Consumption Diagnosis
in Engine Mechanical. |
| • | Low cylinder compression. Refer to Engine Compression Test
in 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. |
|
