Diagnostics · Expert tip
Fuel trims reveal hidden problems
High positive trims = a vacuum leak; negative = rich.
The expert tip
- Long-term trim above +10% often means a vacuum leak
- Below -10% means rich — check MAF, fuel pressure
- Fuel trims point to the system before the part
Source: EFI tuning & diagnostics experts
Apply tips that match your car and manual. For anything safety-critical or high-voltage, use a qualified mechanic.