For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
DEFINITION: Engine delivers less than expected power Little or no increase in speed when accelerator pedal is pushed down part way.
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Perform a bulletin search.
2. If a bulletin that addresses the symptom is found, correct the condition as instructed in the bulletin.

Was a bulletin found that addresses the symptom?

--

Go to Step 16

Go to Step 3

3 | Was visual/physical check performed? | -- | Go to Step 4 | Go to Visual/Physical Checks
4 |

1. Remove the air filter. Refer to Air Filter Element and Air Cleaner Assembly .
2. Inspect the air filter element.
3. Replace the air filter element if necessary.

Was a repair required?

--

Go to Step 16

Go to Step 5

5 |

1. Check fuel pressure. Refer to Fuel System Pressure Test .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 6

6 |

1. Check for water or alcohol contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 7

7 |

1. Using a scan tool, monitor KS system for excessive spark retard activity.
2. If a problem is found, repair as necessary. Refer to Engine Knock Diagnosis in Engine General Information and Mechanical Diagnosis.

Was a problem found?

--

Go to Step 16

Go to Step 8

8 |

1. Check for proper ignition coil output voltage with a J 26792 spark tester:

• | Clip the spark tester to engine ground.

• | 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.

• | 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.

2. If adequate spark is not present at all coils, replace affected coil(s) as necessary. Refer to Ignition Control Module Replacement .

Was a problem found?

--

Go to Step 16

Go to Step 9

9 |

1. Remove the spark plugs.
2. Check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.

Notice: Determine the cause of the oil or gas fouled spark plugs in order to avoid damage to the new spark plugs.

3. If a problem is found, repair as necessary. Refer to On-Vehicle Service in Ignition System.

Was a problem found?

--

Go to Step 16

Go to Step 10

10 |

1. Inspect the ignition coils for cracks or carbon tracking.
2. If a problem is found, replace affected coil(s) as necessary. Refer to Ignition Control Module Replacement .

Was a problem found?

--

Go to Step 16

Go to Step 11

11 |

1. Check PCM grounds for being clean, tight and in their proper locations. Refer to Ground Distribution in Electrical Diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 12

12 |

1. Check the exhaust system for a possible restriction:

• | Inspect exhaust system for damaged or collapsed pipes.

• | Inspect muffler for heat distress or possible internal failure.

• | Check for a possible plugged three-way catalytic converter by checking exhaust system back pressure. Refer to Restricted Exhaust System Check

2. If a problem is found, repair as necessary. Refer to On-Vehicle Service in Exhaust System.

Was a problem found?

--

Go to Step 16

Go to Step 13

13 |

1. Check the Torque Converter Clutch (TCC) for proper operation. Refer to 4L60-E Transmission Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 14

14 |

1. Refer to Engine General Information and Mechanical Diagnosis to check for the following conditions:

• | Low compression.

• | Sticking or leaking valves.

• | Worn camshaft lobe(s).

• | Incorrect valve timing.

• | Bent push rods.

• | Worn rocker arms.

• | Broken valve springs.

2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Go to Step 15

15 |

1. Review all diagnostic procedures within this table.
2. When all procedures have been completed and no malfunctions are found, review/inspect the following:

• | Visual/physical inspection. Refer to Visual/Physical Checks .

• | Scan Tool data. Refer to Engine Scan Tool Data List .

• | Freeze Frame data/Failure Records data.

• | All connections within a suspected circuit and/or system.

3. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 16

Review technical bulletins

16 | Operate the vehicle to duplicate conditions present when the original symptom was noted. Is symptom still present? | -- | Go to Step 3 | System OK