Chevrolet Silverado / GMC Sierra. Manual — part 232
BASE ENGINE MISFIRE WITH COOLANT CONSUMPTION
BASE ENGINE MISFIRE WITH EXCESSIVE OIL CONSUMPTION
assembly.
Stuck valves
Carbon buildup on the valve stem can cause
the valve to not close properly.
Repair or replace, as required.
Excessively worn or mis-aligned timing chain
Replace the timing chain and sprockets, as
required.
Worn camshaft lobes
Replace the camshaft and valve lifters.
Sticking lifters
Replace, as required.
Cut or damaged oil pump screen O-ring seal
which may cause aeration of the engine oil
Repair, as required. Refer to Oil Pressure
Diagnosis and Testing.
Improper operation of the camshaft position
(CMP) actuator and/or control system
Repair, as required. Refer to Camshaft
Position Actuator and Solenoid Valve
Diagnosis and Testing.
Cause
Correction
Faulty cylinder head gaskets and/or cracking
or other damage to the cylinder heads and
engine block cooling system passages
Coolant consumption may or may not cause
the engine to overheat.
1. Inspect for spark plugs saturated by
coolant. Refer to Spark Plug
Inspection .
2. Perform a cylinder leak down test. Refer
to Cylinder Leakage Test.
3. Inspect the cylinder heads and engine
block for damage to the coolant
passages and/or a faulty head gasket.
Refer to Coolant in Combustion
Chamber.
4. Repair or replace, as required.
Cause
Correction
Worn valves, valve guides and/or valve stem
oil seals
1. Inspect the spark plugs for oil deposits.
Refer to Spark Plug Inspection .
2. Repair or replace, as required.
Worn piston rings
Oil consumption may or may not cause the
1. Inspect the spark plugs for oil deposits.
Refer to Spark Plug Inspection .
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
ENGINE NOISE ON START-UP, BUT ONLY LASTING A FEW SECONDS
UPPER ENGINE NOISE, REGARDLESS OF ENGINE SPEED
engine to misfire.
2. Inspect the cylinders for a loss of
compression. Refer to Engine
Compression Test.
3. Perform cylinder leak down and
compression testing to determine the
cause. Refer to Cylinder Leakage Test.
4. Repair or replace, as required.
Cause
Correction
Incorrect oil filter without anti-drainback
feature
Install the correct oil filter.
Incorrect oil viscosity
1. Drain the oil.
2. Install the correct viscosity oil.
High valve lifter leak down rate
Replace the lifters, as required.
Worn crankshaft thrust bearing
1. Inspect the crankshaft end play.
2. Inspect the thrust bearing and
crankshaft.
3. Repair or replace, as required.
Damaged or faulty oil filter bypass valve
The bypass valve is now internal to the oil
filter.
1. Inspect the oil filter bypass valve for
proper operation.
2. Repair or replace, as required.
Cause
Correction
Low oil pressure
1. Perform an oil pressure test. Refer to
Oil Pressure Diagnosis and Testing.
2. Repair or replace, as required.
Loose and/or worn valve rocker arm
attachments
1. Inspect the valve rocker arm, bolt, and
pedestal.
2. Repair or replace, as required.
Worn or damaged valve rocker arm
1. Inspect the rocker arm for wear or
missing needle bearings
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
2. Replace the valve rocker arms, as
required.
Bent or damaged push rod
Inspect the following components and
replace, as required:
The valve rocker arm
The valve push rod
The valve lifter
The valve lifter guide
The piston
Inspect the top of the pistons for valve
contact. If the top of the piston shows valve
contact, replace the piston and pin assembly.
Improper lubrication to the valve rocker
arms
Inspect the following components and repair
or replace, as required:
The valve rocker arm
The valve push rod
The valve lifter
The oil filter bypass valve
The oil pump and pump screen
The engine block oil galleries
Broken valve spring
Replace the valve spring and spring shim.
Worn or dirty valve lifters
Replace the valve lifters, as required.
Improper operation of the camshaft position
(CMP) actuator and/or control system
Repair, as required. Refer to Camshaft
Position Actuator and Solenoid Valve
Diagnosis and Testing.
Stretched or broken timing chain and/or
damaged sprocket teeth
Replace the timing chain and sprockets.
Worn engine camshaft lobes
1. Inspect the engine camshaft lobes.
2. Replace the camshaft and valve lifters,
as required.
Worn valve guides or valve stems
Inspect the following components and repair,
as required:
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
LOWER ENGINE NOISE, REGARDLESS OF ENGINE SPEED
The valves
The valve guides
Stuck valves
Carbon on the valve stem or valve seat may
cause the valve to stay open.
Inspect the following components and repair,
as required:
The valves
The valve guides
Cut or damaged oil pump screen O-ring seal
which may cause aeration of the engine oil
Repair, as required. Refer to Oil Pressure
Diagnosis and Testing.
Cause
Correction
Low oil pressure
1. Perform an oil pressure test. Refer to
Oil Pressure Diagnosis and Testing.
2. Repair or replace damaged components,
as required.
Worn accessory drive components
Abnormalities such as severe cracking,
bumps or missing areas in the accessory drive
belt and/or misalignment of system
components.
1. Inspect the accessory drive system.
2. Repair or replace, as required.
Loose or damaged crankshaft balancer
1. Inspect the crankshaft balancer.
2. Repair or replace, as required.
Detonation or spark knock
Verify the correct operation of the ignition
controls system. Refer to Symptoms -
Engine Controls .
Loose torque converter bolts
1. Inspect the torque converter bolts and
flex plate.
2. Repair or replace, as required.
Loose or damaged flywheel or flex plate
Repair or replace the flywheel or flex plate.
Oil pump screen loose, damaged, or
restricted
1. Inspect the oil pump screen.
2. Repair or replace, as required.
Excessive piston-to-cylinder bore clearance
1. Inspect the piston and cylinder bore.
2. Repair, as required.
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
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