For 1990-2009 cars

## Base Engine Misfire Diagnosis Table B

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Engine Performance diagnosis procedures are covered in Engine Controls and should be consulted for diagnosis of any Driveability, Emissions, or Service Engine Soon lamp complaint. Notice: The following diagnosis information covers common problems and possible causes. When the proper diagnosis is made, the problem should be corrected by adjustment, repair or part replacement as required. Refer to the appropriate section of the manual for these procedures

• | Refer to Engine Controls - General Information.

• | Refer to Engine Controls - Fuel Injection (MF1).

This diagnostic table will isolate any engine misfire due to a mechanical problem such as a faulty camshaft, leaking headgasket, etc. However, this table will not isolate a crossed injector wire, faulty injector, or any other component failure that may cause a misfire. Therefore, the On-Board Diagnostic System Check must be performed first, in order to ensure the correct table is followed for diagnosis of a misfire. Refer to Engine Controls first, then, if necessary, refer to this table.

1 |

1. With the engine running, try to determine if the noise is timed to the crankshaft speed or the camshaft speed.
2. Using a timing light, two knocks per flash is the crankshaft or one knock per flash is the camshaft.

Is the noise timed to the crankshaft speed?

--

Go to Step 2

Go to Step 3

2 |

1. Remove the rod bearings and inspect the bearings and the journals for wear.
2. If the parts are OK, remove the crankshaft and inspect the main bearing and journals for wear.
3. Replace the parts as necessary.

Does the engine continue to misfire?

--

Go to Step 3

System OK

3 | Check to see if the noise is timed to the camshaft speed. Is the noise timed to the camshaft speed? | -- | Go to Step 5 | Go to Step 4
4 |

1. Inspect for loose accessory attachments, the flywheel, or the torque converter.
2. Tighten or adjust as necessary.

Does the engine continue to misfire?

--

Go to Step 5

System OK

5 |

1. Remove the intake manifold. Refer to Intake Manifold Replacement (Upper) .
2. Rotate the engine and measure the Valve lifter movement in the bore.
3. Compare the measurement with the specifications in Engine Mechanical Specifications .

Is the camshaft within specifications?

--

Go to Step 7

Go to Step 6

6 | Replace the camshaft. Refer to Camshaft Replacement . Does the engine continue to misfire? | -- | Go to Step 7 | System OK
7 |

1. Remove the Valve rocker arms, the pushrods, and the Valve lifters.
2. Inspect the parts for excessive wear or damage.
3. Replace the parts as necessary.

Are the repairs complete?

--

System OK

--