Base Engine Misfire Diagnosis Table A
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 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 | Are there any obvious mechanical noises? | -- | Go to Base Engine Misfire Diagnosis (Table B) | |||||
2 | Visually inspect the spark plugs, the wires, and the hoses for proper hook up or damage. Is there any damage or improperly connected wires or hoses? | -- | ||||||
3 | Repair or replace the parts as necessary. Do the symptoms still exist? | -- | System OK | |||||
4 | Remove and inspect the spark plugs. Are any spark plugs contaminated with the engine coolant? | -- | ||||||
5 | Are the spark plugs contaminated with engine oil? | -- | ||||||
6 |
Do the symptoms still exist? | -- | System OK | |||||
7 | Remove and inspect the intake manifold and the intake manifold gasket. Refer to Intake Manifold Replacement (Upper) . Are the components damaged? | -- | ||||||
8 | Replace the parts as necessary Do the symptoms still exist? | -- | System OK | |||||
9 | Remove and inspect the cylinder head. Refer to Cylinder Head Replacement. Are the valve guides or the seals damaged? | -- | ||||||
10 | Remove and inspect the piston, the piston rings, and the cylinder for wear. Are the piston components damaged? | -- | ||||||
11 | Perform a cylinder leak test. Does the engine pass the cylinder leak test? | -- | ||||||
12 |
Are both vacuum readings the same? | -- | ||||||
13 | Inspect each vacuum operated accessory/vacuum line and repair any open or leaking components. Do the symptoms still exist? | -- | System OK | |||||
14 | Using a spray bottle, lightly spray the spark plug wires and the Ignition Control Module while listening to the engine. Did the engine stumble or fail? | -- | ||||||
15 | Replace the spark plug wires and/or the Ignition Control Module . Do the symptoms still exist? | -- | System OK | |||||
16 | Remove the intake manifold and carefully inspect the intake manifold gasket and the TBI gasket. Is there any apparent damage or problem with the gaskets or the sealing surface? | -- | ||||||
17 | Repair or replace the damaged components. Do the symptoms still exist? | -- | System OK | |||||
18 | With the intake manifold removed, rotate the engine and measure the camshaft lobe lift. Is the camshaft within specifications? | -- | ||||||
19 | Replace the camshaft. Refer to Camshaft Removal . Does the symptom still exist? | -- | System OK | |||||
20 | If the problem is still suspected to be mechanical, remove the engine and perform a complete disassembly and inspection. Is the symptom repaired? | -- | System OK | Go to Base Engine Misfire Diagnosis (Table B) | ||||
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
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 |
Is the noise timed to the crankshaft speed? | -- | ||||||
2 |
Does the engine continue to misfire? | -- | System OK | |||||
3 | Check to see if the noise is timed to the camshaft speed. Is the noise timed to the camshaft speed? | -- | ||||||
4 |
Does the engine continue to misfire? | -- | System OK | |||||
5 |
Is the camshaft within specifications? | -- | ||||||
6 | Replace the camshaft. Refer to Camshaft Replacement . Does the engine continue to misfire? | -- | System OK | |||||
7 |
Are the repairs complete? | -- | System OK | -- | ||||
