P0301 on Buick: How to Diagnose & Fix
Cylinder 1 Misfire Detected
3 Buick models · 3 documented issues · 1 critical · $150-$7,500 repair
P0301 on Buick by model: symptoms, diagnosis and fix
The 1.4L LUV turbo uses a single four-tower ignition coil cassette that sits on the valve cover and fires all four cylinders. Heat cycling cracks the coil body or its boots, and the cassette can lose spark on one or more cylinders at once - a Bob Is The Oil Guy thread on an Encore 1.4T misfire and multiple BuickForums P0300 threads trace the misfire to the coil pack (often with worn plugs) after the PCV vacuum-leak possibility is ruled out. Cylinder 3 is the most frequently flagged (P0303). Because the cassette is one part, a failing coil can present as a random multi-cylinder misfire rather than a single dead cylinder.
Common Symptoms
- Flashing or steady check engine light with P0300/P0301-P0304
- Rough idle and shaking
- Hesitation and loss of power under boost
- Misfire worse when engine is hot
How to Fix
Rule out the PCV/intake-manifold vacuum leak first (fuel trims), then check plug gap and coil resistance. The fix is a new coil cassette (roughly $120-$250 for the part, about an hour of labor) and a fresh set of the correct iridium plugs. Dealer repair is typically $300-$500. Avoid bargain coil packs - repeat failures are common.
Sources for this issue (3)
Like other GM direct-injected engines, the Regal's 2.0T and 2.4L DI engines accumulate carbon deposits on the back of the intake valves because fuel no longer washes the valves clean. Over tens of thousands of miles this causes cold-start misfires, rough idle, hesitation, and reduced power and economy. It is a well-documented owner complaint on the turbo cars in particular.
Common Symptoms
- Cold-start misfire / stumble
- Rough idle
- Hesitation on acceleration
- Reduced power and fuel economy
- Misfire codes
How to Fix
Perform a walnut-blasting / manual intake valve cleaning (or chemical induction service in milder cases). Updated engine-management software and periodic intake cleaning help slow recurrence; catch-can installation reduces future buildup.
Sources for this issue (1)
The 4.6L Northstar V8 in 2006-2011 Lucerne CXS/Super (and STS, DTS, Cadillac SLS) is known for head-bolt thread pull from the aluminum block. Bolts back out of the block (rather than head gasket failing outright), allowing combustion gases into the coolant. Symptoms: coolant loss, white smoke, overheating, eventually no-start.
Common Symptoms
- white smoke
- coolant loss
- overheating
- sweet exhaust smell
- rough running
How to Fix
Northstar "time-sert" head bolt repair is the durable fix — block must be removed (engine out or in some cases above-engine work), threads drilled out, larger steel inserts installed. $3,500-$6,000 specialist labor. Some owners try "Block-Tite" / sealants as a band-aid; not durable. Watch coolant level monthly.
Sources for this issue (1)
P0301 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0301 mean on a Buick?
P0301 stands for "Cylinder 1 Misfire Detected." P0301 means the engine computer detected a misfire specifically in cylinder 1 — the spark didn't ignite the fuel properly, or the fuel/air mix didn't burn as it should. The computer detects this by sensing tiny variations in crankshaft speed each time a cylinder fires. A misfire wastes fuel, raises emissions, and can damage the catalytic converter if it's severe or persistent (a flashing check engine light usually warns of active, converter-damaging misfires). Because the code points to one specific cylinder, the cause is usually an ignition, fuel, or compression problem isolated to that cylinder. On Buick it is documented across 3 models: Encore, Regal, Lucerne.
What are the most common causes of P0301?
The most common causes of P0301 are: Worn or fouled spark plug in cylinder 1, Failed ignition coil or coil pack for cylinder 1, Faulty or clogged fuel injector for cylinder 1, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire (on applicable engines), Low compression (worn rings, leaking or burnt valve, head gasket), Carbon buildup on intake valves, Wiring or connector fault to the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0301 on a Buick?
Published repair estimates on Buick range from $150 to $7,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0301 on a different make?
View P0301 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.