what is fuel trim?

[spyderturbo98]

my check engine light came on while i was driving on my 98 gst spyder the other day and i hooked up the error code reader and it says my fuel trim is malfunctioning. would anyone pls tell me what is these fuel trim all about? thanks in advance ! peace!

 

[blackGSX2g]

Fuel trim is how the engine bases how much fuel to put in at a certain point. It should tell you if it was LTFT or STFT, or Long Term Fuel Trim / Short Term Fuel Trim. The short term is based off of your o2 sensor, whereas the long term is based off of stored RPM values. My guess would be that the code was for STFT due to either an o2 sensor problem (easy to test) or if you have a piggyback fuel control system, it might just be reacting to that.

 

[spyderturbo98]

now i have an idea how to troubleshoot my car but how do i check my 02 sensor though...thanks again.