Fuel Trim Archives - AutoSuccessOnline
Air Filters and Fuel Trim Diagnostics

As engine conditions change, fuel trims will change. Here’s what you need to know to diagnose modern engine problems.

Fuel trim is the adjustment the engine computer makes to the fuel mixture to maintain a balanced air/fuel ratio.
LTF and STF Fuel Trim Feedback Loops: Rich, Lean and in Between

Air/fuel ratios can range from 13:1 to 22:1, but no matter what the ratio, there’s a fuel trim cell that addresses them.

Understanding Fuel Trim Theory and Operation

The modern engine measures two things extremely well, the amount of air going into the combustion chamber with the MAF sensor, and the byproducts that are generated by the combustion event with the oxygen sensor. These measurements allow the engine’s computer to put the right amount of fuel and spark into the cylinder to give the most efficient and cleanest combustion event.