P0300 on Pontiac
Random/Multiple Cylinder Misfire Detected
P0300 on Pontiac vehicles indicates random/multiple cylinder misfire detected. Au7o has documented this code across 7 Pontiac models — most commonly on Bonneville, Firebird, G6. P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. Typical repair costs on Pontiac range from $50 to $4,500, depending on the specific model and root cause.
Common Causes of P0300
- •Worn or fouled spark plugs (across cylinders)
- •Vacuum or intake air leak
- •Weak fuel pump, clogged fuel filter, or low fuel pressure
- •Failing ignition coils or worn spark plug wires
- •Dirty or faulty mass airflow (MAF) sensor
- •Clogged or dirty fuel injectors
- •Faulty crankshaft/camshaft position sensor
- •Low compression or EGR/PCV system faults
P0300 on Pontiac by Model
Pontiac Bonneville(1 issue)
- Bonneville 3800 V6 Lower Intake Manifold (LIM) Gasket Failure1995-2005
1995-2005 Bonneville with the 3800 Series II / III V6 (L36 NA or L67 supercharged) suffers the same LIM gasket failure that hit Buick Park Avenue/LeSabre, Olds 88, Chevy Monte Carlo, etc. Plastic intake material softens under coolant exposure (especially Dex-Cool); coolant migrates into the valley and oil. Catastrophic if undetected.
Pontiac Firebird(1 issue)
- Firebird LT1 Optispark Distributor Failure1993-1997
1993-1997 Firebird/Trans Am with the LT1 5.7L V8 (same engine in Camaro Z28, Corvette C4, and some Buick Roadmaster/Caprice/Impala SS) suffers infamous Optispark distributor failure. The distributor sits at the front of the engine behind the water pump — coolant leaks from the water pump (or condensation from the front of the engine) drip directly into the Optispark and short the optical sensors. Symptoms: misfire, no-start, rough running in wet weather.
Pontiac G6(1 issue)
- G6 2.4L Ecotec (LE5/LAT) Timing Chain Stretch2007-2010
The 2.4L Ecotec LE5 in 2007-2010 G6 (and shared Cobalt SS, Malibu, HHR, Saturn Aura/Ion, Solstice) develops timing chain stretch — a very well-documented engineering issue across Ecotec forums and independent shops. Root cause: GM's original Oil Life Monitor allowed intervals up to 12,000 miles, starving the chain. Note: while GM issued Special Coverage Adjustment 11340C covering timing chain stretch on the 3.6L LFX/LLT V6, the 2.4L Ecotec did NOT receive the same blanket warranty extension. Some owners obtained goodwill repairs through dealer-level escalation.
Pontiac Grand Am(1 issue)
- Grand Am 3.4L V6 Upper/Lower Intake Gasket Failure1999-2005
The 3.4L LA1 "3400 SFI" V6 in 1999-2005 Grand Am, Alero, Malibu, Venture, Montana, Aztek, Rendezvous, Impala has a notorious upper/lower intake gasket failure mode similar to the 3800 V6 but with a different gasket part. Coolant leaks externally (under the throttle body area), into the lifter valley, and/or onto the timing cover. Often co-fails with the plastic upper intake plenum cracking.
Pontiac Grand Prix(1 issue)
- Grand Prix 3800 V6 Lower Intake Manifold (LIM) Gasket Failure1997-2008
1997-2008 Grand Prix with the 3800 V6 (NA L36 or supercharged L67) — same LIM gasket failure mode as Bonneville and Buick variants. Particularly common on the supercharged GTP because higher boost pulls coolant past the eroded gasket faster.
Pontiac Montana(1 issue)
- Montana 3.4L V6 Intake Gasket — Same as Grand Am1999-2005
Same 3.4L LA1 V6 upper/lower intake gasket failure as Grand Am. The U-body minivans (Pontiac Montana, Chevy Venture, Olds Silhouette) all share the engine and the failure pattern. Often presents earlier on the minivans due to higher load duty cycles.
Pontiac Vibe(1 issue)
- Vibe 1.8L (1ZZ-FE) Oil Consumption — Coked Piston Rings2003-2008
2003-2008 Pontiac Vibe (and Toyota Matrix/Corolla — all NUMMI-built) with the 1.8L 1ZZ-FE engine commonly develops excessive oil consumption (often 1 qt per 1,000 miles or worse) due to stuck/coked piston oil-control rings. Note: this engine was NOT covered by the well-known Toyota oil-consumption class-action lawsuit — that case (settled in 2014/2015 with warranty extension ZE7 through Oct 2016) applied to the 2.4L 2AZ-FE engine (used in 2009+ Vibe 2.4 and many Toyota models). The 1ZZ-FE issue is well-documented but never received GM or Toyota corporate coverage.
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View P0300 across all makes →Frequently Asked Questions
What does P0300 mean on Pontiac?▼
P0300 stands for "Random/Multiple Cylinder Misfire Detected." P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. On Pontiac specifically, this code is documented across 7 models.
What causes P0300 on Pontiac vehicles?▼
Common causes on Pontiac: Worn or fouled spark plugs (across cylinders), Vacuum or intake air leak, Weak fuel pump, clogged fuel filter, or low fuel pressure, Failing ignition coils or worn spark plug wires, Dirty or faulty mass airflow (MAF) sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0300 on a Pontiac?▼
Repair costs on Pontiac range from $50 to $4,500, depending on the specific model and root cause.
Which Pontiac models have P0300 documented?▼
Au7o has documented P0300 on 7 Pontiac models: Bonneville, Firebird, G6, Grand Am, Grand Prix, Montana, Vibe.