MEDIUM RISK
Common symptoms
- See page for quick checks
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.
- Vacuum leak
- Dirty throttle body
- MAF/MAP error
- PCV fault
- EGR sticking (diesel)
Quick checks (fast, low-cost)
Fast checks you can do with basic tools before buying parts.
- Check intake hoses and clamps.
- Clean throttle body and perform adaptation (if applicable).
- Scan fuel trims and idle control status.
- Check PCV valve function.
- Check for EGR-related codes.
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
- Fix air leaks before replacing sensors.