Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Engine Performance diagnostic 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 assist in engine misfire diagnosis due to a mechanical problem such as a faulty camshaft or leaking headgasket. Base engine timing is assumed to be correct and, that acceptable fuel is being used. This table will not identify a crossed injector wire, faulty injector, coil, driver, etc., or any other component failure or perceived misfire with no driveability symptoms (i.e. chipped reluctor ring with a DTC set or Service Engine Soon Light illuminated). 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 Engine Noise Diagnosis | |||||
2 | Visually inspect valve train components spark plugs, wires, and hoses for proper hook up or damage. Is there any damaged components 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 engine coolant? | -- | ||||||
5 | Are the spark plugs contaminated with engine oil? | -- | ||||||
6 | Check valve stem oil seals and valve guides for wear. Are the valve guides or the seals damaged? | -- | ||||||
7 | Repair or replace valve stem oil seal and valve guides as necessary. Does the symptoms still exist? | -- | System OK | |||||
8 | Remove and inspect the intake manifold and the intake manifold gasket. Refer to Intake Manifold Removal . Are the intake manifold or the intake manifold gasket damaged? | -- | ||||||
9 | Replace the parts as necessary Do the symptoms still exist? | -- | System OK | |||||
10 | Remove and inspect the cylinder head. Refer to Cylinder Head Cleaning and Inspection . Are the valve guides or the seals damaged? | -- | ||||||
11 | Remove and inspect the piston, the piston rings, and the cylinder for wear. Are the piston components damaged? | -- | ||||||
12 | Perform a cylinder leak test. Does the engine pass the cylinder leakdown test? | -- | Go to Engine Unit Repair | |||||
13 |
Are both vacuum readings the same? | -- | ||||||
14 | Inspect each vacuum operated accessory/vacuum line and repair any open or leaking components. Do the symptoms still exist? | -- | System OK | |||||
15 | Using a spray bottle, lightly spray the spark plug wires and the ignition coils while listening to the engine. Did the engine stumble or stall? | -- | ||||||
16 | Replace the spark plug wires and/or the ignition coils. Do the symptoms still exist? | -- | System OK | |||||
17 | Remove the intake manifold and carefully inspect the intake manifold gasket. Is there any apparent damage or problem with the gaskets or the sealing surface? | -- | ||||||
18 | Repair or replace the damaged components. Do the symptoms still exist? | -- | System OK | |||||
19 | Rotate the engine and measure the camshaft lobe lift. Is the camshaft within specifications? | -- | ||||||
20 | Replace the camshaft. Refer to Camshaft Replacement . Does the symptom still exist? | -- | System OK | |||||
21 | 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 Engine Electrical | ||||
