Combating Carbon Build-up in Bentley Engines
Bentley vehicles, renowned for their luxury and performance, share many underlying engine technologies with high-performance Volkswagen Group brands (including Audi and VW). As a result, they are susceptible to similar issues with carbon buildup, injectors, intake manifolds, EGR, DPF, and the fuel system.
Carbon Build-Up issues
Cause:
Bentley models, especially those with direct injection engines, are prone to carbon buildup on intake valves. This occurs because fuel is injected directly into the combustion chamber, so it does not wash over and clean the intake valves. Oil vapours and blow-by gases from the PCV system further contribute to sticky carbon deposits.
Symptoms:
- Rough idle
- Loss of power
- Misfires
- Decreased fuel efficiency
- Check engine light
Known Models Affected:
- Bentley Continental GT (V8 and W12 engines)
- Bentley Flying Spur
- Bentley Bentayga
Solutions:
- Walnut Blasting: The most effective method for removing carbon from intake valves, recommended every 50,000–80,000 km.
- Chemical Intake Cleaning: Products sprayed into the intake can help as a preventative, but are less effective once heavy buildup is present.
- Oil Catch Can: Installing a catch can reduces oil vapour entering the intake, slowing carbon accumulation.
- High-Quality Fuel and Oil: Using top-tier fuel and premium oil can reduce deposit formation.
Injectors Issues
Cause:
Fuel injectors can clog from carbon and gum deposits, or fail due to wear and tear or poor fuel quality.
Symptoms:
- Engine misfires
- Poor acceleration
- Hard starts
- Check engine light
- Fuel leaks (can also be due to deteriorated seals or lines)
Known Models Affected:
- Continental GT
- Flying Spur
- Bentayga
Solutions:
- Injector Cleaning: Use of professional fuel system cleaners or ultrasonic cleaning.
- Injector Replacement: Required if cleaning does not resolve the issue.
- Regular Use of Top-Tier Fuel: Helps prevent injector fouling.
Intake Manifold Issues
Cause:
Carbon and oil deposits can accumulate in the intake manifold, especially in engines frequently driven on short trips or with faulty PCV systems.
Symptoms:
- Rough idle
- Loss of power
- Engine running rich
Solutions:
- Intake Manifold Cleaning: Manual cleaning during carbon service or as part of major maintenance.
- Preventative Maintenance: Regular use of fuel additives and induction cleaning every 15,000 miles can help.
EGR System Issues
Cause:
EGR systems recirculate exhaust gases to lower emissions, but can become clogged with soot and carbon. The EGR temperature sensor, located between the intake manifold and exhaust, is a known failure point.
Symptoms:
- Failed emissions test
- Pinging or knocking noises
- Check engine light
- Rough idle
Solutions:
- EGR Valve/Sensor Cleaning or Replacement: Regular inspection and cleaning; replace faulty sensors promptly.
DPF Filter Issues
Cause:
Diesel Bentleys are equipped with DPFs that can clog due to incomplete regeneration cycles, excessive soot, or short-trip driving.
Symptoms:
- DPF warning light
- Loss of power
- Sluggish acceleration
- Black smoke from the exhaust
- Difficulty starting
- Reduced fuel economy
Solutions:
- DPF Regeneration: Regular highway driving allows for passive regeneration.
- Manual DPF Cleaning: Professional cleaning may be required for severe blockages.
- DPF Replacement: Necessary if cleaning/regeneration fails.
Fuel System Issues
Common Problems:
- Fuel Pump Failures: Can cause sputtering, power loss, or starting issues.
- Fuel Leaks: Often due to deteriorated fuel lines, faulty injectors, or damaged fuel tank seals.
- Fuel Quality Issues: Poor or contaminated fuel can cause misfires, knocking, or reduced efficiency.
Solutions:
- Regular Inspection: Check for leaks, corrosion, and fuel line integrity.
- Prompt Repairs: Address leaks and pump failures immediately for safety and reliability.
- Use of Recommended Fuel: Always use fuel that meets Bentley’s specifications.
- Fuel Filter Replacement: As part of routine maintenance.
Solutions
- Walnut blasting: Mechanically clean intake valves every 50,000-80,000 km.
- Hydrogen carbon cleaning: Non-invasive method for removing deposits.
- Use high-quality, Top-tier fuel to minimise carbon buildup.
- Perform regular “Italian tune-ups” (high-speed highway driving) to help burn off deposits.
- Clean the EGR valve periodically to prevent clogging and maintain proper exhaust gas recirculation.
- For diesel models, ensure proper DPF regeneration through highway driving or DPF Filter cleaning.
- Regular maintenance, including oil changes and filter replacements.
Preventative Measures
- Annual or 15,000-mile induction cleaning to prevent heavy carbon buildup.
- Add fuel system treatment at every oil change to reduce deposit formation.
- Change oil and filter regularly and use only high-quality, manufacturer-approved products.
- Routine visual inspections for leaks or corrosion in the fuel system.
- Address warning lights and performance issues promptly to avoid more severe engine damage.
Bentley vehicles, like other high-performance luxury cars with direct injection and advanced emissions systems, require vigilant maintenance to prevent and address carbon buildup, injector clogging, manifold and EGR issues, DPF blockages, and fuel system faults. Regular professional servicing, use of high-quality fuels and lubricants, and prompt attention to warning signs are essential to preserve performance and reliability.
Carbon Build-Up Related OBD-II Diagnostic Trouble Codes
The following OBD-II codes may indicate carbon buildup issues in your engine.
Use our searchable table to identify and address potential problems:
| Code | Description | Symptoms | Affected System |
|---|---|---|---|
| P246C | Diesel Particulate Filter - Soot Accumulation for Bank 1 | Check engine light | DPF |
| P246B | Diesel Particulate Filter - Soot Accumulation for Bank 2 | Check engine light | DPF |
| P2463 | Diesel Particulate Filter Restriction - Soot Accumulation | Check engine light, reduced power, limp mode activation | DPF |
| P2459 | Diesel Particulate Filter Regeneration Frequency Too High | Check engine light | DPF |
| P2458 | Diesel Particulate Filter Regeneration Duration Too Long | Check engine light | DPF |
| P244A | Diesel Particulate Filter Differential Pressure Too Low | Check engine light | DPF |
| P242F | Diesel Particulate Filter Regeneration Incomplete | Check engine light, poor acceleration | DPF |
| P2176 | Throttle Actuator Control System - Forced Limited Power | Reduced power, check engine light | Manifold |
| P2008 | Intake Manifold Runner Control Stuck Closed | Check engine light, poor acceleration | Manifold |
| P2007 | Intake Manifold Runner Control Stuck Open | Check engine light, rough idle | Manifold |
| P2006 | Intake Manifold Runner Control Actuator Performance Problem | Similar to P2004 symptoms | Manifold |
| P2004 | Intake Manifold Runner Control (IMRC) Actuator Range/Performance Problem | Check engine light, reduced engine performance | Manifold |
| P2002 | Diesel Particulate Filter Efficiency Below Threshold (Bank 1) | Check engine light, reduced fuel efficiency, possible limp mode | DPF |
| P0421 | Warm Up Catalyst Efficiency Below Threshold (Bank 1) | Similar to P0420 symptoms | Carbon Build-Up |
| P0420 | Catalyst System Efficiency Below Threshold (Bank 1) | Check engine light, failed emissions test | Carbon Build-Up |
| P0404 | EGR Control Range/Performance Problem | Check engine light, rough idling, hesitation in acceleration, poor fuel economy | EGR |
| P0403 | EGR Control Circuit Malfunction | Check engine light | EGR |
| P0402 | EGR Flow Excessive | Check engine light, surging at idle | EGR |
| P0401 | EGR Flow Insufficient | Check engine light, engine knocking, poor acceleration | EGR |
| P0400 | EGR Flow Malfunction | Check engine light, rough idling, reduced power | EGR |
| P0304 | Cylinder 4 Misfire Detected | Similar to P0301 symptoms | Carbon Build-Up & Injector |
| P0303 | Cylinder 3 Misfire Detected | Similar to P0301 symptoms | Carbon Build-Up & Injector |
| P0302 | Cylinder 2 Misfire Detected | Similar to P0301 symptoms | Carbon Build-Up & Injector |
| P0301 | Cylinder 1 Misfire Detected | Rough running, poor acceleration | Carbon Build-Up & Injector |
| P0300 | Random/Multiple Cylinder Misfire Detected | Rough idle, engine shaking, reduced power | Carbon Build-Up & Injector |
| P0230 | Fuel Pump Primary Circuit Malfunction | Hard starting, stalling while driving | Fuel System |
| P0206 | Injector Circuit Malfunction - Cylinder 6 (if applicable) | Similar to P0201 symptoms | Injector |
| P0205 | Injector Circuit Malfunction - Cylinder 5 (if applicable) | Similar to P0201 symptoms | Injector |
| P0204 | Injector Circuit Malfunction - Cylinder 4 | Similar to P0201 symptoms | Injector |
| P0203 | Injector Circuit Malfunction - Cylinder 3 | Similar to P0201 symptoms | Injector |
| P0202 | Injector Circuit Malfunction - Cylinder 2 | Similar to P0201 symptoms | Injector |
| P0201 | Injector Circuit Malfunction - Cylinder 1 | Check engine light, rough idle, poor acceleration | Injector |
| P0200 | Injector Circuit/Open | Active check engine light, engine misfires, rough running | Injector |
| P0183 | Fuel Temperature Sensor Circuit High Voltage | Check engine light; possible performance issues | Fuel System |
| P0182 | Fuel Temperature Sensor Circuit Low Voltage | Check engine light; possible performance issues | Fuel System |
| P0174 | System Too Lean (Bank 2) | Increased fuel consumption and decreased performance | Fuel System & Injector & Manifold |
| P0172 | System Too Rich (Bank 1) | Black exhaust smoke, poor performance, increased fuel consumption | Fuel System |
| P0171 | System Too Lean (Bank 1) | Check engine light, poor acceleration | Carbon Build-Up & Fuel System |
| P0106 | Manifold Absolute Pressure (MAP) Sensor Range/Performance Problem | Check engine light, poor acceleration, rough idle | Manifold |
| P0101 | Mass Air Flow (MAF) Sensor Range/Performance Problem | Check engine light, reduced power, poor fuel economy | Manifold |
| P0093 | Fuel System Large Leak Detected | Check engine light, rough running, decreased performance | Fuel System |
| P0090 | Fuel Pressure Regulator Control Circuit Malfunction | Check engine light, poor fuel economy | Fuel System |
| P008B | Low Pressure Fuel System Pressure - Too High | Check engine light, rough idle, reduced power | Fuel System |
| P008A | Low Pressure Fuel System Pressure - Too Low | Check engine light, poor acceleration, engine stalling | Fuel System |