P0303 on Lexus
Cylinder 3 Misfire Detected
P0303 on Lexus vehicles indicates cylinder 3 misfire detected. Au7o has documented this code across 3 Lexus models — most commonly on IS, NX, RC. This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. Typical repair costs on Lexus range from $250 to $1,000, depending on the specific model and root cause.
Common Causes of P0303
- •Worn or fouled spark plug in cylinder 3
- •Failed or weak ignition coil on cylinder 3
- •Bad spark plug wire or boot (where applicable)
- •Clogged or leaking fuel injector for cylinder 3
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Wiring or connector fault at the coil or injector
P0303 on Lexus by Model
Lexus IS(2 issues)
- Carbon Buildup on Intake Valves (2.0T)2016-2022
The direct-injected 2.0L turbo four-cylinder in the IS200t/IS300 accumulates heavy carbon deposits on the intake valves since fuel is not sprayed over the valves to clean them. This leads to rough idle, hesitation under acceleration, and reduced power output typically between 40,000-80,000 miles.
- Valve Cover Gasket Leaks Causing Oil Smell and Misfire Risk2001-2005
Aging valve cover gaskets on the 2JZ-GE commonly harden and leak, allowing oil to seep onto the cylinder head, spark plug tube seals, and exhaust side of the engine. Owners often notice a burnt-oil smell, visible oil around the valve covers, and occasional misfires if oil contaminates ignition components. This is one of the most common age-related engine leaks on the first-gen IS300.
Lexus NX(1 issue)
- Intake Valve Carbon Deposits on the 8AR-FTS Turbo Beyond 60,000 Miles2015-2021
The 8AR-FTS 2.0 turbo in the NX 200t and NX 300 is a direct-injected engine, and Lexus direct-injection engines have a long-standing record of fouling intake valves with carbon because fuel never washes across the back of the valve. Lexus partially mitigated this on the 8AR-FTS with D-4S dual injection - a secondary set of port injectors that does spray the intake valves - which is why this engine is markedly better than a direct-injection-only design and why deposits show up later rather than early. It is not eliminated, however: NX owners posting valve inspections past roughly 60,000 miles document meaningful carbon accumulation on the intake valves, and the symptom set is the classic one - rough cold idle, misfires, hesitation and a check engine light. Buyers of higher-mileage AZ10 NX 200t/300 cars should treat this as an inspection item, not an assumption of failure. This is specific to the 8AR-FTS; the NX 300h hybrid's 2AR-FXE and the second-generation engines are not the same case.
Lexus RC(1 issue)
- Carbon Buildup on Intake Valves (2.0T)2016-2022
The direct-injected 2.0L turbo in the RC200t and RC300 accumulates carbon deposits on the intake valves identically to the IS with the same engine. Without port injection to wash the valves, carbon buildup causes progressive performance degradation starting around 40,000 miles.
Looking for P0303 on a different make?
View P0303 across all makes →Frequently Asked Questions
What does P0303 mean on Lexus?▼
P0303 stands for "Cylinder 3 Misfire Detected." This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. On Lexus specifically, this code is documented across 3 models.
What causes P0303 on Lexus vehicles?▼
Common causes on Lexus: Worn or fouled spark plug in cylinder 3, Failed or weak ignition coil on cylinder 3, Bad spark plug wire or boot (where applicable), Clogged or leaking fuel injector for cylinder 3, Vacuum or intake air leak affecting that cylinder. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0303 on a Lexus?▼
Repair costs on Lexus range from $250 to $1,000, depending on the specific model and root cause.
Which Lexus models have P0303 documented?▼
Au7o has documented P0303 on 3 Lexus models: IS, NX, RC.