OBD-II Code P0272 — What It Means & How to Fix It

What Does This Error Mean?

P0272 means Cylinder 4 is not contributing its expected share of engine power — also called a cylinder contribution or balance fault. Unlike a full misfire code (P0304), this means Cylinder 4 is firing but producing noticeably less power than the other cylinders. The engine computer detects this by monitoring small changes in crankshaft speed after each cylinder fires. Symptoms include a subtle engine vibration, rough idle, reduced power, and slightly worse fuel economy.

Affected Models

All vehicles 1996+
Common in GM V6 and V8 engines with balance testing capability
Common in Ford V8 and EcoBoost engines
Common in higher-mileage vehicles with worn ignition components

Common Causes

Fouled or worn spark plug on Cylinder 4 causing weak, incomplete combustion
Failing ignition coil on Cylinder 4 producing a weak spark
Partially clogged fuel injector on Cylinder 4 not delivering enough fuel
Low compression on Cylinder 4 due to worn piston rings, valves, or a head gasket issue
Small vacuum leak near the Cylinder 4 intake port leaning out the air/fuel mixture

How to Fix It

Inspect and replace the Cylinder 4 spark plug first. Pull the plug and examine it — a fouled, worn, or cracked plug is the most common cause of a single-cylinder contribution fault and the cheapest fix available.

While you're at it, check all plugs. If Cylinder 4's plug looks worse than the others, that's a strong diagnostic clue.
Swap the Cylinder 4 ignition coil with a neighboring cylinder's coil, then clear the code and drive. If the fault follows the coil to its new location, the coil is the problem. Replace it.

This swap-test method avoids spending money on a new coil before confirming it's bad.
Have the Cylinder 4 fuel injector professionally tested for flow rate and spray pattern. A partially clogged injector delivers less fuel than needed, causing the cylinder to underperform without fully misfiring.

Ultrasonic injector cleaning at a shop typically costs $15–$30 per injector and can restore lost flow.
Inspect the intake manifold area near Cylinder 4 for vacuum leaks. A small unmetered air leak leans out just that one cylinder. Spray carburetor cleaner carefully around the intake runners and listen for RPM changes at idle.

Never spray flammable cleaner near hot exhaust components. Work carefully and have a fire extinguisher nearby.
Perform a compression test on all cylinders and compare results. Cylinder 4 should be within 10% of the highest reading. Low compression on Cylinder 4 alone indicates internal wear requiring professional evaluation.

If you get low compression, follow up with a leak-down test to narrow down whether it's rings, valves, or a gasket.

When to Call a Professional

If replacing the spark plug and coil doesn't clear P0272, have a mechanic perform a compression and leak-down test on Cylinder 4. Low compression means internal engine wear that cannot be fixed with tune-up parts. Continuing to drive with a contribution fault will eventually cause a full misfire and risk catalytic converter damage.

Frequently Asked Questions

What is the difference between P0272 and P0304?

P0304 is a full misfire — Cylinder 4 is failing to fire properly and the engine noticeably stumbles. P0272 is a contribution fault — Cylinder 4 fires, but produces less power than it should. Think of P0272 as an early warning. If ignored, P0272 often progresses into P0304.

Can I drive with P0272?

Yes, briefly — but don't ignore it. A contribution fault won't strand you immediately, but it causes extra wear on the other cylinders, reduces fuel economy, and typically worsens over time. Fix it promptly to avoid escalating into a more expensive misfire repair.

How much does it cost to fix P0272?

Spark plug set: $50–$150 installed. Ignition coil: $50–$200 installed. Injector cleaning: $50–$100. Injector replacement: $150–$400. Engine compression/internal repairs: $1,000–$4,000+.