GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Express 🢒 Engine 🢒 Engine Mechanical - 4.3L 🢒 Base Engine Misfire without Internal Engine Noises

Cause

Correction

High oil pressure
    • Verify oil pressure. Refer to Oil Pressure Diagnosis and Testing .
    • Repair or replace damaged components as required.

Worn, damaged, or improperly installed accessory drive belt - severe cracking, bumps or missing segments

A misfire DTC may be present without an actual misfire condition.
    • Inspect the accessory drive system components.
    • Repair or replace damaged components as required. Refer to Drive Belt Replacement .

Worn, damaged, or improperly installed accessory drive system components

A misfire DTC may be present without an actual misfire condition.
    • Inspect the accessory drive system components.
    • Repair or replace damaged components as required.

Damaged, loose or improperly installed crankshaft balancer

A misfire DTC may be present without an actual misfire condition.
    • Inspect the crankshaft balancer.
    • Repair or replace damaged components as required. Refer to Crankshaft Balancer Replacement .

Worn, damaged, or improperly installed crankshaft reluctor wheel

A worn or damaged crankshaft reluctor wheel can result in different symptoms depending on the severity and location of the wear or damage.

    • Systems with electronic communications, DIS or coil per cylinder, and severe reluctor ring damage may exhibit periodic loss of crankshaft position, stop delivering a signal, and then re-sync the crankshaft 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 DTC P0300 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. A DTC P0300 or P0336 may be set.
    • Inspect the crankshaft position sensor.
    • Inspect the crankshaft reluctor wheel.
    • Inspect the crankshaft.
    • Repair or replace damaged components as required.

Damaged, loose or improperly installed engine flywheel

A misfire DTC may be present without an actual misfire condition.
    • Inspect the flywheel.
    • Repair or replace damaged components as required. Refer to Engine Flywheel Replacement .

Damaged, improperly installed or restricted exhaust system, collapsed or dented pipes, plugged mufflers or malfunctioning catalytic converters

A DTC may be present without an actual fault condition.
    • Inspect the exhaust system components.
    • Repair or replace damaged components as required.

Worn, damaged or improperly installed vacuum hoses
    • Inspect the vacuum system components.
    • Repair or replace damaged components as required.

Damaged or improperly installed MAP sensor, sealing grommet nicked, torn or missing
    • Inspect the MAP sensor.
    • Repair or replace damaged components as required.

Damaged or improperly installed throttle body
    • Inspect the throttle body.
    • Repair or replace damaged components as required.

Damaged or improperly installed intake manifold
    • Inspect the intake manifold.
    • Repair or replace damaged components as required.

Damaged or improperly installed cylinder head

Oil consumption may or may not cause the engine to misfire.
    • Inspect the spark plugs. Refer to Spark Plug Inspection .
    • Verify engine compression. Refer to Engine Compression Test .
    • Inspect the cylinder heads.
    • Inspect the engine block.
    • Repair or replace damaged components as required.

Worn, damaged or loose valve rocker arm
    • Inspect the valve rocker arms.
    • Repair or replace damaged components as required.

Worn, damaged or loose valve rotator
    • Inspect the valve rotators.
    • Repair or replace damaged components as required.

Worn, damaged, loose or broken valve spring
    • Inspect the valve springs.
    • Repair or replace damaged components as required.

Worn, damaged or stuck valve, carbon on the valve stem or valve seat
    • Inspect the valves.
    • Inspect the valve guides.
    • Repair or replace damaged components as required.

Worn or damaged valve guide
    • Inspect the valve guides.
    • Inspect the valves.
    • Repair or replace damaged components as required.

Worn, damaged, loose or bent valve push rod
    • Inspect the valve push rods.
    • Repair or replace damaged components as required.

Worn, damaged or dirty valve lifter
    • Inspect the valve lifters.
    • Inspect the camshaft.
    • Repair or replace damaged components as required.

Worn or damaged camshaft lobe
    • Inspect the camshaft.
    • Inspect the valve lifters.
    • Repair or replace damaged components as required.

Worn, damaged or loose timing chain and sprockets
    • Inspect the timing chain and sprockets.
    • Repair or replace damaged components as required.

Worn, damaged or improperly installed piston

Pistons must be installed with the mark, or dimple, on the top of the piston, facing the front of the engine; piston pins must be centered in the connecting rod pin bore.

Oil consumption may or may not cause the engine to misfire.
    • Inspect the spark plugs. Refer to Spark Plug Inspection .
    • Verify engine compression. Refer to Engine Compression Test .
    • Inspect the cylinder bores.
    • Inspect the pistons.
    • Inspect the piston pins.
    • Inspect the connecting rods.
    • Repair or replace damaged components as required.