Chevrolet Silverado / GMC Sierra. Manual - part 402
BASE ENGINE MISFIRE WITH ABNORMAL INTERNAL LOWER ENGINE NOISES
components.
Damaged or misaligned timing gears
1. Inspect timing gears.
2. Replace all damaged components.
Worn or faulty camshaft lobes
1. Inspect camshaft lobes.
2. If damaged replace camshaft and all
lifters.
Excessive piston-to-cylinder bore clearance
1. Perform cylinder leak down and
compression tests.
2. Inspect the piston, piston rings and
cylinder bore.
3. Repair or replace all damaged
components.
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. Perform cylinder leak down and
compression tests.
2. Inspect the piston, piston rings and
cylinder bore.
3. Repair or replace all damaged
components.
Overfilled Crankcase
1. Check engine oil level with vehicle on a
level surface.
2. Correct any overfilled condition.
3. Inspect for fuel leaks into the crankcase.
Refer to Fuel in Engine Oil.
4. Repair any fuel leaks.
Condition
Action
Abnormalities (severe cracking, bumps or
missing areas) in the accessory drive belt.
Abnormalities in the accessory drive belt
and/or components may cause engine RPM
variations, noises similar to a faulty lower
engine and also lead to a misfire condition. A
misfire code may be present without an actual
misfire condition.
1. Inspect the accessory drive components.
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
2. Repair or replace all damaged
components.
Worn, damaged, or misaligned accessory
drive components or excessive pulley runout
A misfire code may be present without an
actual misfire condition.
1. Inspect the accessory drive components.
2. Repair or replace all damaged
components.
Loose and/or damaged crankshaft balancer
A misfire code may be present without an
actual misfire condition.
1. Inspect crankshaft balancer and
balancer bolt.
2. Repair or replace all damaged
components.
Loose torque converter bolts
A misfire code may be present without an
actual misfire condition.
1. Inspect torque converter bolts and
flywheel.
2. Repair or replace all damaged
components.
Loose and/or damaged flywheel
A misfire code may be present without an
actual misfire condition.
1. Inspect flywheel and flywheel attaching
bolts.
2. Repair or replace all damaged
components.
Excessive piston-to-cylinder bore clearance
1. Perform cylinder leak down and
compression tests
2. Inspect the piston, piston rings and
cylinder bore.
3. Repair or replace all damaged
components.
Excessive crankshaft thrust bearing clearance Severely worn thrust surfaces on the
crankshaft and/or thrust bearing may permit
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
BASE ENGINE MISFIRE WITH ABNORMAL VALVE TRAIN NOISE
for and aft movement of the crankshaft and
create a misfire code without an actual
misfire condition.
1. Inspect the crankshaft end play and
crankshaft thrust bearings.
2. Repair or replace all damaged
components.
Overfilled crankcase
1. Check engine oil level with vehicle on a
level surface.
2. Correct any overfilled condition.
3. Inspect for fuel leaks into the crankcase.
4. Repair any fuel leaks.
Condition
Action
Loose, worn or damaged rocker arm
1. Inspect valve rocker arm and rocker arm
shaft.
2. Repair or replace all damaged
components.
Loose valve rocker arm attachments
1. Inspect valve rocker arm and rocker arm
shaft.
2. Repair or replace all damaged
components.
Worn or damaged pushrods
1. Inspect the pushrods for excessive wear.
2. Inspect the pushrods for bent condition.
3. Inspect the pushrods for broken tip.
4. Replace pushrod if any damage is found.
Broken valve springs
1. Inspect valve springs.
2. Repair or replace all damaged
components.
Worn and/or damaged valve rotator
1. Inspect valve rotators.
2. Repair or replace all damaged
components.
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
BASE ENGINE MISFIRE WITH COOLANT CONSUMPTION
Sticking valve
Carbon on the valve stem or valve seat may
cause the valve to stick.
1. Inspect valves and valve guides.
2. Repair or replace all damaged
components.
Worn or faulty camshaft lobes
1. Inspect camshaft lobes.
2. If damaged replace camshaft and all
lifters.
Excessive valve lash
1. Check the valve lash adjustment, and
correct if above specifications.
2. Repair or replace all damaged
components.
Inspection
Action
DEFINITION: Base engine misfire with coolant consumption
Preliminary Inspection
Verify that there are no external coolant
leaks. Refer to Loss of Coolant .
Isolate Affected Cylinders
Cylinder balance test with scan tool
Cooling system pressurization
Inspection of glow plugs
Compression test
Cylinder leakdown test
EGR System Inspection
1. Inspect EGR valve and intake system for
evidence of coolant leakage.
2. Replace the EGR cooler if any problem
is found.
Cylinder Head Gasket Leakage
Remove cylinder heads of the affected
cylinder bank and inspect for damage.
Replace components as necessary.
1. Inspect the cylinder heads for cracks and
warpage.
2. Inspect the cylinder block for damage.
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 6.6L - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado