For 1990-2009 cars

#### Hesitation, Sag, Stumble Symptom

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Definition: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually most pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain 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 21

Go to Step 3

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

1. Check Heated Oxygen Sensors (HO2S). The Heated Oxygen Sensor (HO2S) should respond quickly to different throttle position. If they don't, check the HO2S for silicon or other contaminants from fuel or use of improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine , causing a severe driveability problem. For more information, refer to Powertrain Control Module (PCM) and Sensors.
2. If a problem is found, repair as necessary.

Was a repair required?

--

Go to Step 21

Go to Step 5

5 |

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

Was a problem found?

--

Go to Step 21

Go to Step 6

6 | Observe TP angle display on the scan tool while slowly increasing throttle pedal. Does the TP angle display steadily increase from 0% at closed throttle to 100% at WOT? | -- | Go to Step 7 | Go to Step 20
7 | Monitor Long Term Fuel Trim on the scan tool. Is Long Term Fuel Trim significantly in the negative range (Rich condition)? | -- | Go to Step 8 | Go to Step 9
8 |

1. Check items that can cause the engine to run rich. Refer to Diagnostic Aids in Diagnostic Support page of DTC P0172.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 10

9 |

1. Check items that can cause the engine to run lean. Refer to Diagnostic Aids in Diagnostic Support page of DTC P0171.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 10

10 |

1. Check for proper ignition coil output voltage with spark tester J 26792 (ST 125):

• | Clip the spark tester J 6792 to engine ground.

• | Connect J 26792 to an ignition wire then ground spark plug end of ignition wire from companion cylinder. The companion cylinder is the cylinder that shares the same ignition coil.

• | Crank the engine while observing the spark tester J 26792; a crisp blue spark should be observed.

• | Repeat the above steps for each coil.

2. If adequate spark is not present at all coils, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 11

11 | Check for:

1. Loose ignition control module ground. Refer to Electronic Ignition System.
2. Camshaft Position Sensor Signal.
3. 24X Crankshaft Position Sensor Signal.
4. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 12

12 |

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. Refer to Electronic Ignition System in Engine Electrical.

1. Visually/Physically inspect secondary ignition wires. Check for the following conditions:

• | Check all Ignition wire resistances; should be less than the specified value.

• | Ignition wires for cross firing.

• | Ignition wires arcing to ground.

• | Ignition wires for improper routing.

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

Was a problem found?

30 K ohms (30,000 ohms)

Go to Step 21

Go to Step 13

13 |

1. Check ignition coils for cracks or carbon tracking.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 14

14 |

1. Check ignition coil secondary resistance.
2. Replace any coil(s) which are not within the specified values.

Did any coil(s) require replacement?

5K-7K ohms (5000-7000 ohms)

Go to Step 21

Go to Step 15

15 |

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

1. Remove spark plugs and check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits. Refer to Electronic Ignition System.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 16

16 |

1. Check PCM grounds for being clean, tight and in the proper locations. Refer to PCM wiring diagrams in Electrical Diagnosis section 8A.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 17

17 |

1. Check MAF sensor connections.
2. If a problem is found, replace faulty terminals as necessary. Refer to Electrical Diagnosis section 8A for wiring repair procedures.

Was a problem found?

--

Go to Step 21

Go to Step 18

18 |

1. Visually/physically check vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 21

Go to Step 19

19 |

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

• | Visual/physical inspection.

• | Scan Tool data.

• | Freeze Frame data/Failure Records Data.

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

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

Was a problem found?

--

Go to Step 21

Review Technical Service Bulletins

20 | Replace the TP sensor. Is Action complete? | -- | Go to Step 21 | --
21 | Operate the vehicle to duplicate conditions present when the original symptom was noted. Is symptom still present? | -- | Go to Step 3 | Repair Complete