Commodore (VN-VZ) / HSV

1988-2006 / Sedan / Estate / Australia

All Commodore (VN-VZ) / HSV problems All workshop problems

Common Idle and Running Issues

Injector Failure (Ecotec V6)

Symptoms

Misfire on one or more cylinders. Rough idle. Check engine light with misfire codes. Fuel smell from the exhaust. Engine stumbles under acceleration.

Cause

The Ecotec fuel injectors can develop electrical faults (open or short circuit in the coil) or mechanical faults (blocked spray pattern, stuck open, or leaking). High-mileage injectors accumulate deposits that affect spray pattern even if the injector still functions electrically.

Fix

Diagnose with a scan tool, misfire codes identify the affected cylinder.

Swap the suspected injector with one from a known-good cylinder to confirm diagnosis.

Injector cleaning ($15-25 per injector at a specialist) restores most flow-related issues.

Replacement injectors: $40-80 each.

Replace the injector seals (O-rings) whenever an injector is removed, reusing old seals causes fuel leaks.

Cost mentioned in fix

$15-25 per injector$40-80 each

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Other known issues

Common Idle and Running Issues

Rough Idle and Stalling (V6, All Generations)

Engine idles roughly, may stall at traffic lights. RPM fluctuates between 500-1000 rpm at idle. Stalling is worse when the air conditioner is on or at the first stop after a cold start.

Common Engine, V6 (Buick/Ecotec 3.8L, VN-VY)

Intake Manifold Gasket Leak

Coolant leak at the junction of the intake manifold and cylinder heads. May present as coolant loss without a visible external leak (coolant enters the intake ports), or as a coolant stain on the side of the engine. Engine may run rough or misfire if coolant enters the combustion chamber.

Critical Engine, V6 (Buick/Ecotec 3.8L, VN-VY)

Harmonic Balancer Failure (Ecotec, VS onwards)

A wobbling pulley on the front of the crankshaft. Knocking or rattling noise from the front of the engine. The drive belt may track poorly or come off.

Common Engine, V6 (Buick/Ecotec 3.8L, VN-VY)

Supercharger Bypass Valve Failure (L67 supercharged V6)

Loss of boost, rattling from the supercharger, reduced performance. The supercharger may make a whining noise that changes with the valve's operation.

Critical Engine, V6 (Alloytec 3.6L, VZ)

Timing Chain and Guide Failure

Rattling noise on cold start that may persist after warm-up. Check engine light with codes related to camshaft timing. Rough idle, misfiring, loss of power. In severe cases, the engine won't start or runs extremely poorly.

Critical Engine, V6 (Alloytec 3.6L, VZ)

Oil Leaks from Timing Cover

Oil weeping or dripping from the front of the engine, behind the harmonic balancer area.

All Commodore (VN-VZ) / HSV problems