Long Term Fuel Trim (LTFT).
Short Term Fuel Trim (STFT)

"Fuel Trim" is the fine tune control of fuel delivery by the ECU. To accomplish this the ECU increases or
decreases fuel delivery by increasing or decreasing the time that the injectors are open.

By monitoring the primary Oxygen sensor(s) (pre catalytic convertor), engine coolant temperature,
throttle position, air mass volume, engine speed(rpm) and to a lesser extent changes in altitude, humidity,
ambient temperature, fuel quality, etc

A vacuum leak or a bad MAF sensor and O2 sensor will cause you to run rich. disconnect the MAF sensor then start your engine and if it runs much better then the MAF is your issue .

If your reading are over +20% or -20% then you have a problem ,but normally the check engine light will come on and give you a code

Long Term Fuel Trim (LTFT)
This is the control of Injection Pulse Time Open (ti) (also called Injection Pulse Width) over the entire range
of engine operation. It is primarily calculated at idle or low load mid range engine operation and is averaged
over time.
In these idle/low load conditions the amount of fuel variation is small due to the relatively small amount of air
input. The computer monitors the O2 sensor and ADDS or SUBTRACTS approximately 0.001msec to the
injection pulse time (ti) in order to maintain a Lambda = 1. This amount of increase or decrease of the
injection pulse width is known as the Adaptation Value. This is the value output by the ECU when reading
the live data stream.
For example: An LTFT of 1 is the factory spec for a new injector's injection pulse width (time open). This
corresponds to an LTFT Adaptation Value of 0.0.
An LTFT Adaption Value of 0.100 would indicate a wider injection pulse width. This corresponds to a LTFT
of 1.100.
An LTFT Adaption Value of -0.020 would indicate a narrower injection pulse width. This corresponds to a
LTFT of 0.980.
The LTFT is also influence by the Short Term Fuel Trim (STFT).
Short

Short Term Fuel Trim (STFT) Multiplicative
This is the control of the Injection Pulse Time Open over the mid to upper range of engine operation. When
the engine operates at normal or higher load or at higher engine speeds, larger volumes of fuel and air are
needed. In order to maintain a Lambda = 1 in these conditions, the ECU monitors the O2 sensor and
calculated load (see figure 2) and compares the values against the optimal value for the fuel injection pulse
width stored in the drive map. If this base fuel injection pulse width value does not yield a Lambda = 1 at the
O2 sensor for the measured air mass, the computer increases or decreases the pulse width by a percentage
(%) determined by the difference in Lambda from optimal. These percentages have been computed by the
engineers at the factory from extensive dynamometer testing and are stored in a "weighted STFT value
array(1)" in the drive maps. When the STFT reaches the limit of its adjustment it will cause corresponding
decrease or increase to the Long Term Fuel Trim. If the correction to the base value exceeds +25% or -25%
for longer than 10 seconds a DTC is set for rich or lean stop for STFT.

Hear are some conditions that will set adaptations faults and there causes.
Intake air leaks
Incorrect Fuel Pressure
Injector valve defective or coked
Engine Temperature Sensor defective
EGR valve defective
Secondary air leak
Fuel evaporation control system defective or leaking.
Air Mass Meter defective
Vacuum leaks
Oxygen sensor aging (slow response)
Clogged or damaged catalytic converter
Contaminated fuel
Fuel tank ran empty
Combustion altered by a mechanical failure (Spark plugs, compression, intake/exhaust valves, ...etc.)

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Kind regards Greg.