BASE ENGINE MISFIRE WITH ABNORMAL INTERNAL LOWER ENGINE NOISES
Base Engine Misfire with Abnormal Internal Lower Engine Noises
position.
Systems with electronic communication
(DIS or coil per cylinder) and slight
reluctor ring damage may exhibit no
loss of crankshaft position and no
misfire may occur. However, a P0300
DTC may be set.
Systems with mechanical
communications (high voltage switch)
and severe reluctor ring damage may
cause additional pulses and effect fuel
and spark delivery to the point of
generating a P0300 DTC or P0336.
Cause
Correction
Abnormalities (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.
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.
Worn Piston Rings
Oil consumption may or may not cause the
engine to misfire.
Inspect the spark plugs for oil deposits.
Inspect the cylinders for a loss of
compression. Refer to Engine
Compression Test.
2007 Hummer H3
2007 ENGINE Engine Mechanical - 3.7L - H3