For 1990-2009 cars

#### Rough, Unstable, or Incorrect Idle, Stalling Symptom

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Definition: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine.
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to 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 13

Go to Step 3

3 | Perform the careful visual/physical checks as described at the start of Symptoms section. Was the visual/physical check performed? | -- | Go to Step 4 | Go to Important Preliminary Checks
4 |

1. Check the PCM grounds for being clean, tight and proper routing. Use the PCM wiring diagrams in Section 8A .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 5

5 | Observe the Long Term Fuel Trim on the scan tool. Is Long Term Fuel Trim below the specified value (Rich condition)? | 70 2.4L 80 2.2L | Go to Step 6 | Go to Step 7
6 |

1. Check the items that can cause the engine to run rich. Refer to DTC P0172 Fuel Trim System Rich for diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 9

7 | Is the Long Term Fuel Trim above the specified value (Lean condition)? | 165 2.4L 160 2.2L | Go to Step 8 | Go to Step 9
8 |

1. Check the items that can cause the engine to run lean. Refer to DTC P0171 Fuel Trim System Lean .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 9

9 |

1. Check the IAC operation. Perform procedure in DTC P0506 Idle Speed Low diagnostic table.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 10

10 |

1. Check the MAP sensor for proper operation. Refer to Manifold Absolute Pressure Sensor Output Diagnosis for further diagnosis.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 11

11 | Check the injector connections. If any of the injectors are connected to an incorrect cylinder, correct as necessary. Was a problem found? |  | Go to Step 26 | Go to Step 12
12 |

1. Perform the Fuel Injector Solenoid Coil Test or Fuel Injector Balance Test .
2. If a problem is found, repair as necessary.

Was a problem found?

Go to Step 26

Go to Step 13

13 |

1. Check for fuel in pressure regulator vacuum hose.
2. If fuel is present, replace the fuel pressure regulator assembly. Refer to Fuel Pressure Regulator Replacement .
3. If a problem is found, repair as necessary.

Was a problem found?

Go to Step 26

Go to Step 14

14 |

1. Check for proper ignition voltage output with the spark plug jumper wires J 36012 and spark tester J 26792.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 15

15 |

Notice: If spark plugs are gas or oil fouled, determime the cause of the fouling before replacing the spark plugs in order to avoid damage to the new spark plugs.

1. Remove the spark plugs, check for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 16

16 |

1. Check for loose ignition control module ground.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 17

17 |

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

Was a problem found?

--

Go to Step 26

Go to Step 18

18 | Using a scan tool, monitor the TP angle with the engine idling. Is the TP angle at the specified value and steady? | 0% | Go to Step 19 | Go to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage for further diagnosis
19 |

1. Check the Crankcase oil/air separator for proper operation. Refer to Crankcase Ventilation System Diagnosis .
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 20

20 |

1. Check for proper generator voltage output.
2. The voltage should be between the specified values.

Is the voltage between the specified values?

11-16V

Go to Step 21

Go to Powertrain Control Module Controlled Generator Diagnosis

21 |

1. Check for proper A/C operation. A/C clutch should disengage at Wide Open Throttle.
2. If a problem is found, refer to Air Conditioning (A/C) Compressor Clutch Control Diagnosis for further diagnosis.

Was a problem found?

--

Go to Air Conditioning (A/C) Compressor Clutch Control Diagnosis

Go to Step 22

22 |

1. Check for the following engine mechanical items. Refer to Engine Mechanical for diagnosis procedures:

• | Check compression.

• | Sticking or leaking valves.

• | Worn camshaft lobe(s).

• | Incorrect valve timing.

• | Broken valve springs.

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

Was a problem found?

--

Go to Step 26

Go to Step 23

23 |

1. Check for malfunctioning motor mounts. Refer toEngine Mechanical for inspection of mounts.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 26

Go to Step 24

24 |

1. Check the intake valves for valve deposits.
2. If deposits are found, remove as necessary.

Were deposits found on the intake valves?

--

Go to Step 26

Go to Step 25

25 |

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 items:

• | Visual/physical inspection.

• | Scan tool data.

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

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

Is the action complete?

--

Go to Step 26

--

26 | Operate vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK | Go to Step 2