Smoke under load
Smoke appears mainly when accelerating/boosting; can be oil, fuel, or coolant related.
MEDIUM RISK
Common symptoms
- Blue smoke on boost
- Black smoke when flooring it
- Sweet smell/steam
Cost expectations
Typical costs vary by car and region. Use this as a ballpark.
- DIY / parts: £20–£80
- Garage / labour: £80–£250
Most likely causes (ranked)
Start at the top. Rule out the common, cheap causes before expensive ones.
- Turbo oil seal / PCV issue — Oil pushed into intake under boost.
- Overfueling (injector/MAF) — Black smoke; rich mixture.
- Boost leak causing rich — ECU adds fuel for air that leaks out.
- Coolant ingress — White steam; monitor coolant level.
- DPF regen (diesel) — Temporary smoke; check regen behaviour.
Quick checks (fast, low-cost)
Fast checks you can do with basic tools before buying parts.
- Note smoke color (blue/black/white).
- Check oil level change over time and intercooler pipes for oil pooling.
- Scan fuel trims/MAF readings.
- Check coolant level stability.
- Pressure test intake if boost leak suspected.
Recommended tools
These tools make diagnosis faster and stop you buying random parts.
Related fixes
If your symptoms don’t match perfectly, check these next.
What to do next
- Address oil smoke quickly to protect catalyst/DPF.
- If coolant loss accompanies smoke, stop driving and test for head gasket.