Fuel Trim Readings: STFT & LTFT Interpreter
Interpret Your Fuel Trims
What Fuel Trims Mean
Short-term fuel trim (STFT) shows rapid ECU adjustments, while long-term fuel trim (LTFT) tracks the running average. Together they reveal if the engine is running lean (positive trim) or rich (negative trim).
- Normal: Within roughly -5% to +5% total trim.
- Borderline: 5% to 10% suggests a small bias.
- High: Over 10% points to a system issue worth chasing.
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