For 1990-2009 cars

#### Lack of Power, Sluggish or Spongy

Checks | Action
--- | ---
DEFINITION: The engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.
Preliminary Inspections |

• | Refer to Important Preliminary Inspections Before Starting in Symptoms .

• | Search for bulletins.

• | Inspect the ECM grounds for being clean, tight and in the proper locations. Refer to Engine Controls Schematics .

• | Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Filter Element and Air Cleaner Assembly and replace as necessary.

• | Inspect the intake air ducts for the following conditions:

- | Restrictions

- | Improperly installed hoses

- | Leaks

- | Collapsed hoses

Fuel System |

• | Test for proper fuel pressure. Refer to Fuel System Diagnosis .

• | Test for a restricted fuel filter. Refer to Fuel System Diagnosis .

• | Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Test the fuel injectors. Refer to Fuel Injector Balance Test and Fuel Injector Solenoid Coil Test .

• | Inspect the items which can cause an engine to run rich (long term fuel trim near -13 percent). For a rich condition, refer to DTC P0172 Fuel Trim System Rich Bank 1 and DTC P0175 Fuel Trim System Rich Bank 2 .

• | Inspect the items that can cause an engine to run lean (long term fuel trim near 23 percent). For a lean condition, refer to DTC P0171 Fuel Trim System Lean Bank 1 and DTC P0174 Fuel Trim System Lean Bank 2 .

Sensor/System |

• | Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Detonation/Spark Knock .

• | Check for proper operation of the throttle control system components. Use the scan tool special functions to actuate the system. Verify that the throttle opens to 100 percent. With a scan tool. monitor the following throttle control system components:

- | Throttle position sensors

- | Accelerator pedal position sensors

- | Throttle actuator

Ignition System |

• | Test for proper ignition voltage output with a J 26792 spark tester . Refer to Ignition System Check .

• | Test for secondary ignition leakage. Refer to the procedure in the Diagnostic Aids portion of Ignition System Check .

• | Remove the spark plugs and inspect for the following conditions:

- | Correct heat range

- | Wet plugs

- | Cracks

- | Wear

- | Improper gap

- | Burned electrodes

- | Heavy deposits

• | An improper spark plug gap will cause a driveability concern. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement in Engine Electrical.

• | 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 Visual Diagnosis in Engine Electrical:

- | For diagnosis of a rich condition, refer to DTC P0172 Fuel Trim System Rich Bank 1 or to DTC P0175 Fuel Trim System Rich Bank 2 .

- | For diagnosis of coolant contaminated spark plugs, refer to Loss of Coolant in Engine Cooling.

- | For diagnosis of oil fouled spark plugs, refer to Oil Consumption Diagnosis in Engine Mechanical.

Engine Mechanical |

• | Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.

• | Check for incorrect camshaft timing. Refer to Timing Belt Timing Adjustment in Engine Mechanical.

• | For incorrect basic engine parts, inspect the following:

- | Camshafts, refer to Camshaft and Bearings Cleaning and Inspection in Engine Mechanical.

- | Cylinder heads, refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.

- | Pistons, connecting rods or bearings, refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection in Engine Mechanical.

Additional Inspections |

• | Inspect the exhaust system for possible restrictions:

- | The exhaust system for physical damage

- | The mufflers for heat distress or possible internal failure

- | The catalytic converters for possible plugged pipes by comparing the exhaust system back pressure on each side of engine. Refer to Restricted Exhaust System Check .

• | Test for proper operation of the intake resonance switchover valve and the intake plenum switchover valve. Refer to Multi Ram System Diagnosis .

• | Test the transmission torque converter clutch (TCC) for proper operation. Refer to Torque Converter Diagnosis in Automatic Transmission-4L30-E.

• | Check for other transmission related faults that might cause the transmission to operate in a default mode. Refer to Transmission On Board Diagnostic (OBD) System Check in Automatic Transmission-4L30-E.