Base Engine Misfire without Internal Engine Noises
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 and lead to a
misfire DTC. 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 - May lead to a misfire DTC.
A misfire code may be present without an actual misfire
condition.
Inspect the components, and 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
.
Restricted exhaust system
A severe restriction in the exhaust flow can cause significant
loss of engine performance and may set a DTC. Possible
causes of restrictions include collapsed or dented pipes or
plugged mufflers and/or catalytic converters.
Repair or replace as required.
Improperly installed or damaged vacuum hoses
Repair or replace as required.
Improper sealing between the intake manifold and cylinder
heads or throttle body
Replace the intake manifold, gaskets,
cylinder heads, and/or throttle body as
required.
Improperly installed or damaged MAP sensor
The sealing grommet of the MAP sensor should not be torn
or damaged.
Repair or replace the MAP sensor as
required.
Damage to the MAP sensor housing and/or seal
Replace the intake manifold.
Worn or loose rocker arms
The rocker arm bearing end caps and/or needle bearings
should be intact and in the proper position.
Replace the valve rocker arms as required.
Worn or bent pushrods
Replace the pushrods.
Inspect the top of the pistons for valve
contact. If the top of the piston shows
valve contact, replace the piston and pin
assembly.
Stuck valves
Carbon buildup on the valve stem can cause the valve not to
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.
Excessive oil pressure
A lubrication system with excessive oil pressure may lead to
z
Perform an oil pressure test. Refer to
Oil Pressure Diagnosis and
2004 Chevrolet Corvette
2004 ENGINE PERFORMANCE Engine Mechanical (Introduction) - 5.7L - Corvette
Helpmelearn
December-24-07 10:50:08 AM
Page 43
© 2005 Mitchell Repair Information Company, LLC.
