Fuel trim numbers-both long term/and short term

There is no exact number, but there is an expected range for short term (ST) and long term (LT) trims. Generally, fuel trim will fluctuate between negative and positive single digit numbers. Usually they'll stay around positive or negative 5%. But can go as high as 8 or 9% based on the condition of the engine. A normal LT fuel trim reading will appear to stay steady. Under normal conditions, it should be close to 0, positive or negative single digits, too.

Keep in mind, the trims are really the result of what the O2 sensor is telling the computer. If you have a vacuum leak, fuel pressure issues. The computer will try to compensate; thus, it will try adding or removing fuel to the engine. That will change the trims.

Glad to help. Using the scanner, watch how the O2 sensors are reacting.