P0303 on 2014-2019 Land Rover Range Rover Sport: Cylinder 3 Misfire Causes and Fixes

What's Unique About the 2014-2019 Land Rover RANGE ROVER SPORT

While ignition components are the usual suspects for a P0303 code, on this specific JLR platform, the issue can be more complex. Land Rover has issued Technical Service Bulletins (TSBs) indicating that misfire codes, including P0303, can appear due to fuel injection calibration issues, especially on cold starts. Furthermore, TSB SSM74161 shows P0303 can be stored alongside various camshaft timing codes (P054A, P0014, P000B, P0341), sometimes without any noticeable driving problems, pointing towards potential timing system or sensor anomalies rather than a simple spark or fuel issue. These engines are also known for cooling system issues, where failing plastic pipes or water pumps can cause overheating, potentially leading to head gasket leaks that manifest as misfires.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Rough or vibrating idle
• Hesitation or stumbling during acceleration
• Reduced engine power and 'Reduced Engine Performance' message
• Solid or flashing Check Engine Light
• Decreased fuel economy
• Engine running rough when cold
• Noticeable fuel or exhaust smell

Most Likely Causes

1. Faulty Ignition Coil 🔴 High Probability Coil-on-plug ignition systems are common failure points on many modern engines as they age due to heat and vibration. The plastic housings can crack, allowing spark to arc to the cylinder head instead of the spark plug.
   How to confirm: Swap the ignition coil from cylinder 3 with another cylinder (e.g., cylinder 1). Clear the codes and drive the vehicle. If the code changes to P0301, the ignition coil is faulty. Cylinder 3 is on the passenger side, making it relatively accessible.
   Typical fix: Replace the failed ignition coil. Many technicians recommend replacing all coils on the same bank, or all coils and spark plugs at the same time, for preventative maintenance. An owner on a forum resolved their P0303 and P0307 codes by replacing just the one failing coil.
   Est. part cost: $50 - $120
2. Worn or Fouled Spark Plug 🔴 High Probability
   How to confirm: After confirming the coil is good, remove the spark plug from cylinder 3. Inspect it for wear (worn electrode), carbon fouling (black, sooty), oil fouling, or damage. A wet, fuel-smelling plug indicates a lack of spark or an injector issue. A 14mm thin-wall spark plug socket is required for these engines.
   Typical fix: Replace the spark plug. It is best practice to replace all spark plugs at the same time to maintain consistent performance. Land Rover recommends this service every 90,000 miles.
   Est. part cost: $20 - $50
3. Faulty Fuel Injector 🟡 Medium Probability
   How to confirm: Listen to the injector with a mechanic's stethoscope to ensure it's clicking. You can also use a 'noid light' to verify the electrical pulse from the PCM. For a definitive test, swap the injector with another cylinder to see if the misfire follows. This is more labor-intensive than swapping a coil.
   Typical fix: Replace the faulty fuel injector. The fuel system may need to be depressurized. One owner with a persistent cold-start misfire on a similar engine ultimately traced it to a faulty injector after replacing coils and plugs.
   Est. part cost: $100 - $250
4. Fuel Injection Calibration Issue ⚪ Low Probability A known issue documented in TSB LTB01023NAS1 for 2014-2015 models. Misfires may occur only when the engine is cold (coolant temp below 75°C).
   How to confirm: This issue is confirmed if P0316 is present with other misfire codes (like P0303) and the freeze frame data shows a coolant temperature below 75°C.
   Typical fix: A Land Rover dealer or qualified shop needs to update the Powertrain Control Module (PCM) software. This requires JLR-specific diagnostic equipment.
   Est. part cost: $0 (if under warranty) - $200 (shop labor for update)

Rare But Worth Checking

• Low Engine Compression: Can be caused by worn piston rings, a leaking head gasket, or valvetrain problems. A compression test is needed to diagnose this. A forum user noted that on older Land Rover engines, coolant leaks from head gaskets are a concern for middle cylinders. Overheating from a failed water pump or coolant pipe on the AJ126/AJ133 engine is a known cause of head gasket failure.
• Vacuum Leak: A leak in a vacuum hose or intake manifold gasket near cylinder 3 could lean out the air/fuel mixture, causing a misfire. This would typically be accompanied by other lean codes (P0171/P0174) or random misfire code P0300.
• Camshaft Timing/Phaser Issue: As mentioned in TSB SSM74161, P0303 can appear with timing-related codes like P054A, P0014, P000B, and P0341. This points to a more complex mechanical or sensor issue within the variable valve timing system, potentially a faulty VVT solenoid.
• Carbon Buildup on Intake Valves: Direct injection engines, like the AJ126 and AJ133, are prone to carbon buildup on the back of the intake valves over time. This can disrupt airflow into the cylinder, leading to misfires, especially on cold starts. This typically requires professional cleaning (e.g., walnut blasting).

Diagnosis Steps

1. Read the trouble codes with an OBD-II scanner and note any other codes present, especially timing or other misfire codes.
2. Check the freeze frame data to see the engine conditions (coolant temperature, RPM, load) when the misfire occurred. This is critical for identifying cold-start issues mentioned in TSBs.
3. To test the ignition coil, swap the coil from cylinder 3 with one from an easily accessible cylinder (like cylinder 1). Clear the codes and run the engine. If the code returns as P0301, the coil is bad.
4. If the misfire remains on cylinder 3, inspect the spark plug. Look for signs of wear, damage, or fouling. A 14mm thin-wall socket is needed. Replace if necessary.
5. If the coil and plug are good, check the fuel injector. Listen for a consistent clicking sound with a stethoscope. Check the injector's wiring harness for damage or corrosion.
6. Inspect for vacuum leaks around the intake manifold, especially near the runner for cylinder 3.
7. If simple components are ruled out, perform a compression test on cylinder 3 to check for mechanical engine problems like worn rings or a bad valve.
8. If timing codes are present alongside P0303, refer to TSB SSM74161 and investigate the variable valve timing system. This step may require a professional technician.

Parts You'll Likely Need

• Ignition Coil (OEM #LR035532) — This is one of the most frequent causes of a single-cylinder misfire due to failure from heat and age.
  Trusted brands: Bosch, Delphi, NGK, Genuine Land Rover
  OEM price range: $80 - $120
  Aftermarket price range: $40 - $90
• Spark Plug (OEM #LR025605) — Spark plugs are a routine maintenance item and can cause misfires when worn, fouled, or incorrectly gapped. NGK is a common OEM supplier.
  Trusted brands: NGK, Bosch, Genuine Land Rover
  OEM price range: $25 - $50
  Aftermarket price range: $15 - $30
• Fuel Injector (OEM #LR079542) — Less common than ignition parts, but injectors can become clogged or fail electronically, causing a misfire. Often requires replacement in sets if one fails due to age.
  Trusted brands: Bosch, Genuine Land Rover
  OEM price range: $150 - $250
  Aftermarket price range: $100 - $180

Related Codes That Often Appear With This One

• P0300 — Indicates a random/multiple cylinder misfire. If the cause of the P0303 is systemic (like a vacuum leak, bad batch of fuel, or low fuel pressure), other cylinders may misfire as well.
• P0301, P0302, P0304, etc. — Misfire codes for other cylinders. Seeing them together can point to a common cause like bad fuel, a vacuum leak, or a timing issue. A user on landroverforums.com reported P0307 and P0303 together, which was resolved with a new ignition coil.
• P0316 — Indicates a misfire was detected within the first 1000 engine revolutions after startup. TSB LTB01023NAS1 specifically links this code with P0303 on cold starts due to a fuel calibration issue.
• P054A, P0014, P000B, P0341 — These are camshaft position and timing-related codes. TSB SSM74161 notes that P0303 can be stored with these codes, indicating a potential timing system problem rather than a simple ignition fault.

Technical Service Bulletins (TSBs) & Recalls

• SSM74161: Notes that P0303-00 can be stored with camshaft timing DTCs (P054A-00, P0014-71, P000B-00, P0341-00, P0302-00) in the PCM, sometimes with no driveability concerns.
• LTB01023NAS1: Addresses poor running and misfires (P0300-P0308) with P0316 on cold starts (coolant temp < 75°C) on 2014-2015 models, caused by a fuel calibration issue requiring a PCM update.

Platform-Specific Known Issues

• Cold Start Misfires (2014-2015 models): TSB LTB01023NAS1 identifies an issue where a fuel injection calibration problem can cause misfires (P0303 and others) along with code P0316, specifically when the engine coolant temperature is below 75°C. The fix is a PCM software update performed by a dealer.
• Misfire with Camshaft Timing Codes: TSB SSM74161 notes that P0303 can be stored with codes like P054A, P0014, P000B, and P0341, even with no driveability issues. This points to a potential problem with the Variable Valve Timing (VVT) system, likely a faulty solenoid, rather than a typical ignition or fuel fault.
• Owner Experience: Simple Fix: A user on landroverforums.com with an LR3 (which shares engine architecture) experienced multiple misfire codes including P0303. After changing spark plugs with no success, the issue was finally resolved by replacing a single faulty ignition coil with an aftermarket part from AutoZone for around $40.