Diagnostic Information And Procedures; Base Engine Misfire Diagnosis - GMC chevrolet camaro 2000 Service Manual

Engine Engine Mechanical - 3.8L 6-21
Diagnostic Information and Procedures
Base Engine Misfire Diagnosis
Checks Action
Engine performance diagnosis procedures are covered in Engine Controls and should be consulted for diagnosis of any
Driveability, Emissions, or Malfunctioning Indicator Lamp (MIL) concerns.
The following diagnosis covers common concerns and possible causes.
When the proper diagnosis is made, the concern should be corrected by adjustment, repair or replacement as required.
Refer to the appropriate section of the service manual for each specific procedure.
This diagnostic table will assist in engine misfire diagnosis due to a mechanical concern such as a faulty engine camshaft,
worn or damaged bearings or bent valve pushrod.
This tap le ll'lill not isolate. a crossed fuel injector wire, faulty fuel injector or any other driveability component failure that may
cause a misfire. ·
The Powertrain On-Board Diagnostic ~ystem checks must be performed first.
. When using this. table to make a Base Engine Misfire diagnosis, begin with the preliminary information below and then
proceed to the specific category.
Preliminary
Intake Manifold Leaks
Coolant Consumption
1 . Perform OTC P0300 before proceeding with Base Engine Misfire Diagnosis
information .
. OTC P0300 will assist in determining which cylinder or cylinders are misfiring.
2. Perform a visual inspection of the following:
• A loose or improperly installed engine flywheel or crankshaft balancer
• Worn, damaged or misaligned accessory drive system components
3. Listen to the engine for any abnormal internal engine noises.
4. Inspect the engine for acceptable oil pressure.
5. Verify if the engine has excessive oil consumption.
6. Verify if the engine has excessive coolant consumption.
7. Perform a compression test on the engine.
An intake manifold that has a vacuum leak may cause a misfire.
Inspect for t.he following:
• Improperly installed or damaged vacuum hoses
• Faulty .or improperly installed lower intake manifold and/or gaskets
• c.racked or damaged lower intake manifold
• Improperly installed MAP sensor
The sealing grommet of the MAP sensor should not be torn or damaged
• Improperly installed throttle body or damaged gasket
• Warped intake manifold
• Warped or damaged cylinder head sealing surface
Coolant consumption may or may not cause the engine to overheat.
Inspect for the following:
• External coolant leaks
• Faulty cylinder head gasket
• Warped cylinder head
• Cracked cylinder head
• Damaged engine block