Engine Performance (A8)Question 96 of 120
Technician A says a positive long-term fuel trim of +20 percent means the PCM is adding fuel to correct a lean condition. Technician B says positive trim means the engine is running rich. Who is correct?
a.Technician A only
b.Both A and B
c.Technician B only
d.Neither A nor B
Explanation
Positive fuel trim means the computer is adding fuel to correct a lean condition from a vacuum leak, low fuel pressure, or a dirty MAF. Technician B is wrong because rich conditions produce negative trims. Comparing short- and long-term trims helps pinpoint the fault.
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