Base Engine Misfire with Abnormal Internal Lower Engine Noises
BASE ENGINE MISFIRE WITH ABNORMAL VALVE TRAIN NOISE
Base Engine Misfire with Abnormal Valve Train Noise
Cause
Correction
Abnormalities, such as severe cracking, bumps or missing
areas in the accessory drive belt
Abnormalities in the accessory drive system 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.
Replace the drive belt. Refer to
Drive
Belt Replacement - Accessory
.
Worn, damaged, or mis-aligned accessory drive components or
excessive pulley runout
A misfire code may be present without an actual misfire
condition.
Inspect the components, repair or
replace as required.
Loose or improperly installed engine flywheel or crankshaft
balancer
A misfire code may be present without an actual misfire
condition.
Repair or replace the flywheel and/or
balancer as required.
Refer to
Engine Flywheel Replacement
or
Crankshaft Balancer Replacement
.
Worn piston rings
Oil consumption may or may not cause the engine to misfire.
z
Inspect the spark plugs for oil
deposits. Refer to
Spark Plug
Inspection
in Engine Controls -
5.7L.
z
Inspect the cylinders for a loss of
compression. Refer to
Engine
Compression Test
.
z
Perform cylinder leak down and
compression testing to determine
the cause. Refer to
Cylinder
Leakage Test
.
z
Repair or replace as required.
Worn crankshaft thrust bearings
Severely worn thrust surfaces on the crankshaft and/or thrust
bearing may permit fore and aft movement of the crankshaft
and create a DTC without an actual misfire condition.
Replace the crankshaft and bearings as
required.
Cause
Correction
Worn or loose rocker arms
The rocker arm bearing end caps and/or
needle bearings should be intact within the
rocker arm assembly.
Replace the valve rocker arms as required.
Worn or bent pushrods
z
Replace the pushrods.
z
Inspect the top of the pistons for valve contact. If
2004 Chevrolet Corvette
2004 ENGINE PERFORMANCE Engine Mechanical (Introduction) - 5.7L - Corvette
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December-24-07 10:50:09 AM
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