Chevrolet Silverado / GMC Sierra. Service 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