Your 2022 GMC Acadia trembles at idle and acceleration feels off. The check engine light confirms your suspicion with P0302—cylinder 2 is misfiring. A single-cylinder misfire like this typically points to cylinder-specific components rather than engine-wide problems, making diagnosis more straightforward.
Understanding P0302
P0302 indicates the Engine Control Module detected misfire events specifically on cylinder 2. Unlike P0300 (random misfire), this code pinpoints the problem to one cylinder, suggesting an issue with that cylinder's ignition, fuel delivery, or mechanical condition.
The 2022 Acadia's 3.6L V6 is a proven engine, but like any engine, individual cylinders can develop problems. Cylinder 2's location on the front bank (passenger side, middle position) makes it accessible for diagnosis.
The Usual Suspects
Spark plug failure on cylinder 2 is the most common cause. Plugs can crack, foul, or wear enough to misfire before the recommended 100,000-mile interval. Cylinder 2's plug is no more prone to failure than others, but if it fails first, that's where you'll see problems.
Ignition coil failure disables spark for that cylinder completely. Each cylinder has its own coil, and individual coil failure causes cylinder-specific misfires. Coils can fail from age, heat exposure, or manufacturing defects.
Fuel injector problems—clogged, stuck, or electrically failed—prevent proper fuel delivery to cylinder 2. A cylinder can't fire properly without the correct fuel charge.
Compression loss from worn rings, damaged valve seals, or head gasket breach on that cylinder reduces combustion pressure enough to cause misfires.
Diagnostic Process
Swap the coil from cylinder 2 to another cylinder (say, cylinder 4) and clear codes. Drive until the code returns. If P0304 appears instead of P0302, the coil is bad. If P0302 returns, the coil is not the problem.
Perform the same swap test with the spark plug if the coil tests good. Move cylinder 2's plug to another cylinder and see if the misfire follows.
Test injector operation by listening for clicking with a stethoscope or using a noid light to verify electrical pulse. Swap injectors if possible to confirm whether the injector is the culprit.
Perform a compression test on cylinder 2 and compare to other cylinders. More than 10% variation suggests mechanical problems with that cylinder.
Repair Costs
Spark plug replacement for all six (recommended when replacing one): $150-$300 including labor.
Ignition coil replacement: $50-$150 for the part plus $50-$100 labor. Many owners replace all coils at similar mileage preventively.
Fuel injector replacement: $100-$250 per injector plus $100-$200 labor depending on access.
If compression issues exist, repairs range from $500 for valve seals to $2,000+ for head gasket or ring repair.
Why Vibration Occurs
A misfiring cylinder disrupts the engine's balance. The 3.6L V6 is designed to fire in a specific sequence that creates smooth operation. When one cylinder fails to contribute, the engine shakes. The roughness is most noticeable at idle when there's no road vibration to mask it.