P0301: How to Diagnose & Fix — Cylinder 1 Misfire Detected
248 vehicles · 40 makes · $20-$25,000 repair
How to diagnose and fix P0301: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Mazda RX-8 · 2004–2012
The Renesis rotary engine in the RX-8 is infamous for apex seal wear and failure, leading to catastrophic compression loss. Apex seals maintain the combustion chamber seal between the rotor and housing. Heat, carbon deposits, and inadequate lubrication cause seals to wear, chip, or break. Compression testing below 6.5 kg/cm2 indicates rebuild is needed. This is the single most common and feared RX-8 issue.
Common Symptoms
- Hard starting, especially when warm (hot start failure)
- Progressive loss of power over time
- Excessive exhaust smoke (white or blue)
- Failed compression test (below 6.5 kg/cm2 on any face)
- Engine floods easily and will not restart
How to Fix
Engine rebuild with new apex seals, side seals, corner seals, and rotor housings if scored. Rebuild by a rotary specialist is essential - general mechanics often lack the expertise. Prevention: premix 2-stroke oil with fuel (1 oz per gallon), rev the engine to redline regularly to keep seals seated, never shut off a warm engine without letting it idle for 30 seconds.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Rotarytronics rotary compression testerOEMRotarytronics Rotary Compression Tester
Rotary-specific compression measurement before an engine rebuild decision Fitment/availability: The direct manufacturer product page showed a $199.99 base price and is designed to report individual rotary chamber pulses.
- Atkins Rotary ARE64 2004-2011 RX-8 rotor/seal kitOEMAtkins Rotary ARE64
Configurable internal seal kit only after specialist teardown measurements Fitment/availability: The direct specialist page identifies ARE64 for 2004-2008 and 2009-2011 RX-8 and provides selectable apex/corner-seal options; it showed $67…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipRev to redline daily to keep apex seals properly seated - babying a rotary kills it faster
- TipCompression test every 15,000 miles to monitor seal health - RX8Club.com apex seal FAQ
Hyundai Sonata · 2011–2019
The Theta II engine can seize due to metal debris blocking oil flow to connecting rod bearings. Hyundai issued recalls and extended warranties. Affected engines may need replacement.
Common Symptoms
- Knocking noise from engine
- Engine stalling
- Check engine light
- Loss of power
- Engine seizure
How to Fix
Check VIN for active recalls - Hyundai provides free engine replacement for affected vehicles. Install the knock sensor detection system (KSDS) software update that monitors for bearing wear. Change oil every 5,000 miles. If engine fails and under warranty, replacement is free. Out of warranty replacement: $4,000-8,000.
Owner tips & cautions
- TipDIY repairs can save significantly - dealer charges $4,000-8,000 but DIY costs are typically 50-70% less
- WarningThis is a high-severity issue - ignoring it can lead to costly repairs or safety concerns. Address it promptly.
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
Sources for this issue (1)
- NHTSA Recall 17V-224recall
Volkswagen Golf · 2008–2021
All EA888 direct-injection 2.0T engines suffer from carbon buildup on the intake valves because fuel is injected directly into the combustion chamber rather than sprayed over the valves. Without fuel washing, oil vapors from the PCV system bake onto the intake valves, reducing airflow and causing drivability issues. Buildup becomes noticeable around 40,000-60,000 miles. VW addressed this in the Gen3 EA888 (2015+) by adding port injection, but the problem persists to some degree in all direct-injection variants.
Common Symptoms
- Rough idle
- Hesitation on acceleration
- Misfires (codes P0300-P0304)
- Reduced fuel economy
- Loss of power especially at low RPM
- Check engine light
How to Fix
Walnut shell blasting of intake valves is the most effective treatment ($400-700 at a shop). Some owners use chemical cleaning kits (Revive Turbo Cleaner, CRC GDI IVD Intake Valve Cleaner). Prevention: install a catch can to reduce oil vapor reaching the valves, and perform walnut blasting every 40,000-60,000 miles. The Gen3 EA888 (2015+) with dual injection has reduced but not eliminated the problem.
Sources for this issue (1)
Land Rover Freelander · 2002–2005
Subaru Outback · 1999–2010
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P0301 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 P0301 mean?
P0301 stands for "Cylinder 1 Misfire Detected." P0301 means the engine computer detected a misfire specifically in cylinder 1 — the spark didn't ignite the fuel properly, or the fuel/air mix didn't burn as it should. The computer detects this by sensing tiny variations in crankshaft speed each time a cylinder fires. A misfire wastes fuel, raises emissions, and can damage the catalytic converter if it's severe or persistent (a flashing check engine light usually warns of active, converter-damaging misfires). Because the code points to one specific cylinder, the cause is usually an ignition, fuel, or compression problem isolated to that cylinder.
What are the most common causes of P0301?
The most common causes of P0301 are: Worn or fouled spark plug in cylinder 1, Failed ignition coil or coil pack for cylinder 1, Faulty or clogged fuel injector for cylinder 1, Vacuum or intake air leak affecting that cylinder, Bad spark plug wire (on applicable engines), Low compression (worn rings, leaking or burnt valve, head gasket), Carbon buildup on intake valves, Wiring or connector fault to the coil or injector. The specific cause varies by vehicle.
How much does it cost to fix P0301?
Repair costs for P0301 range from $20 to $25,000, depending on the vehicle and root cause.
Which vehicles are affected by P0301?
Au7o has documented P0301 across 248 vehicle models from 40 manufacturers: Acura, Alfa Romeo, Audi, BMW, Buick, Cadillac, Chevrolet, Chrysler, Citroen, Dodge, Ford, GMC, Genesis, Honda, Hyundai, Infiniti, Jaguar, Jeep, Kia, Land Rover, Lexus, Lincoln, MINI, Mazda, Mercedes-Benz, Nissan, Peugeot, Pontiac, Porsche, RAM, Renault, SEAT, Saab, Saturn, Skoda, Subaru, Suzuki, Toyota, Volkswagen, Volvo.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.