What does a positive short term fuel trim mean?

Positive fuel trim values If the displayed fuel trim value is a positive number, it means that the ECU is increasing the injector pulse width to add fuel to the air/fuel mixture to enrich the mixture because the input data it is receiving tells it that the mixture is too lean.

What causes negative long term fuel trim at idle?

The MAF sensor overestimates airflow at idle, which causes the negative fuel trim values. It then underestimates airflow at cruising speeds, which accounts for the positive fuel trim values. The MAF sensor overestimates airflow at idle, which causes the negative fuel trim values.

What causes high positive short term fuel trim?

Short-term fuel trim happens as a result of changes in the oxygen levels of exhaust gases. An oxygen sensor monitors the flow and generates a signal that is proportional to the oxygen levels in the gases.

What causes negative STFT?

Negative fuel trim percentages indicate the PCM is attempting to lean out the fuel mixture, to compensate for a perceived rich condition. STFT and LTFT percentages are the adjustments made by the PCM to maintain the 14.7:1 ratio.

What does Ltft B2 mean?

LTFT B2 is Long Term Fuel Trim engine cylinder Bank 2.

What causes rich Ltft?

Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and …

Why is my long term fuel trim so high?

Why are the fuel trim numbers high? If LTFT or total fuel trim is greater than plus 10\%, the PCM thinks the air/fuel ratio is too lean and it’s adding fuel to bring STFT control to the correct range.

What causes long term fuel trim?

Possible causes: Vacuum leak in a vacuum hose, intake gasket or air duct after the MAF sensor. Check using propane enrichment or leak test with a smoke machine. Clogged fuel injectors.

What is a bad long term fuel trim?

What does negative short term fuel trim mean?

The short-term fuel trim (STFT) refers to immediate changes in fuel occurring several times per second. A negative fuel trim percentage indicates the PCM is removing fuel while a positive percentage indicates the PCM is adding fuel.