What is the normal range for short-term fuel trim?

[McBrady]

Short-term fuel trim values between -5.2% to -8.6% are considered normal. Short-term fuel trim is a real-time correction control of fuel injection quantity based on the oxygen sensor's feedback regarding the air-fuel mixture's richness or leanness in previous working cycles. Through continuous short-term fuel trim adjustments, the mixture concentration is maintained as close as possible to the theoretical air-fuel ratio. Factors affecting the fuel trim coefficient include engine misfires, exhaust flow restrictions, low fuel pump pressure, or clogged fuel injectors, which can be inspected accordingly. If the combined value of long-term and short-term fuel trim adjustments exceeds 5%, it may indicate potential issues such as clogged injectors, eroded spark plugs, poor fuel quality, malfunctioning mass air flow sensors, or overdue fuel filter replacement.