P0302 on Buick: How to Diagnose & Fix
Cylinder 2 Misfire Detected
3 Buick models · 3 documented issues · 1 critical · $150-$7,500 repair
P0302 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)
P0302 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 P0302 mean on a Buick?
P0302 stands for "Cylinder 2 Misfire Detected." This code means the engine computer has detected a misfire specifically in cylinder 2, meaning that cylinder isn't completing combustion properly on some firing events. The computer watches tiny variations in crankshaft speed to spot when a cylinder fails to fire, and a misfire means the air-fuel mixture isn't igniting correctly — usually from a spark, fuel, or compression problem in that cylinder. You may feel a stumble, rough idle, shaking, loss of power, or a flashing check-engine light, and persistent misfires can damage the catalytic converter. Because it names a single cylinder, the fault is often a component serving just cylinder 2, like its coil, plug, or injector. On Buick it is documented across 3 models: Encore, Regal, Lucerne.
What are the most common causes of P0302?
The most common causes of P0302 are: Worn or fouled spark plug (cylinder 2), Failed ignition coil or coil-on-plug (cylinder 2), Clogged or faulty fuel injector (cylinder 2), Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt/bent valve, head gasket), Damaged spark plug wire or boot (if equipped), Carbon-tracked or cracked coil/plug causing spark loss, Faulty PCM/ECM driver (rare). The specific cause varies by vehicle.
How much does it cost to fix P0302 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 P0302 on a different make?
View P0302 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.