Cylinder 3 Misfire Detected
What it means
P0303 means the engine control module detected a misfire specifically in cylinder 3 — the fuel isn't burning properly in that cylinder, so the engine runs rough and loses power. The usual culprit is a worn spark plug or failing ignition coil on that cylinder. A sustained misfire can overheat and damage the catalytic converter, so address it promptly.
Can I keep driving? Not for long — a flashing check-engine light means cylinder 3 is actively misfiring; drive as little as possible to avoid catalytic converter damage.
Real-world scan data
Appears alongside · share of P0303 scans
Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.
Common symptoms
What you'll notice
- Check-engine light on (often flashing during an active misfire)
- Rough idle, shaking, or stumbling
- Reduced power and hesitation on acceleration
- Occasional stalling at idle
Common causes
Most likely first
- Worn spark plug in cylinder 3Likely
- Failing ignition coil on cylinder 3Common
- Clogged or leaking fuel injector on cylinder 3Common
- Vacuum leak affecting that cylinderLess often
- Low compression in cylinder 3 (valve or ring wear)Less often
- Faulty ECM (rare)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to confirm the miss is on cylinder 3.
- Swap the coil and plug with an adjacent cylinder — if the misfire follows, you've found it.
- Replace the worn spark plug and/or ignition coil for that cylinder.
- Test the injector for that cylinder (resistance and spray).
- If it persists, run a compression test to check for mechanical wear. Clear and re-test.
P0303 by make
Based on commonly reported failure patterns across owner and repair communities, not on our scan data.
BMW
On BMWs, failing ignition coils and worn spark plugs are a common reason for a misfire on cylinder 3, particularly on turbocharged engines. Replace plugs and check the coils together.
Ford
On Ford engines with coil-on-plug ignition, such as the 5.4L Triton, a failing coil or worn spark plug on cylinder 3 is a commonly reported cause. Swapping the coil with a neighbouring cylinder is an easy way to see if the misfire follows it.
Honda
On Hondas, a worn plug or coil on cylinder 3 is common, and on V6 models with cylinder deactivation, fouled plugs from oil can also play a part. Check the plug condition before swapping parts.
Hyundai
On Hyundai models, a misfire on cylinder 3 can be a simple coil or plug problem, but on 2.4L four-cylinder engines it can also be a sign of internal engine wear. Get it checked soon if there is knocking or oil use.
Kia
On Kia models, a misfire on cylinder 3 can be a simple coil or plug problem, but on 2.4L four-cylinder engines it can also be a sign of internal engine wear. Get it checked soon if there is knocking or oil use.
Nissan
On Nissans, ignition coils and spark plugs on cylinder 3 are the usual culprits, particularly on V6 models. Swap coils between cylinders to see if the misfire follows.
Subaru
On Subarus, plugs and coils on cylinder 3 are the first things to check. On older 2.5L boxer engines, a head gasket leak into a cylinder can also cause misfires.
Toyota
On Toyotas, a failed ignition coil or worn spark plug on cylinder 3 is the usual cause. Swapping the coil with a neighbouring cylinder shows quickly whether the misfire moves.
Volkswagen
On VW and Audi turbo engines, a failing ignition coil on cylinder 3 is a very common cause. Swapping coils between cylinders is a cheap way to confirm it.
FAQ
Quick answers
Is it safe to drive with P0303?+
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