I want to make sure I understand the fuel trims on my 90 Talon

[nestamon99]

Yes guys, I have tried to use the search button but my question was never answered. I want to make sure that I am reading the fuel trims correctly.

Fuel Trim HI: 116%
Fuel Trim Mid: 103%
Fuel Trim Low: 84%

If I am reading it correctly, the computer is adding more fuel to the high trim than the mid. The low trim is to rich is trying to take away fuel? Is that correct or the I have it backwards??

 

[pneumo]

You have it right. If the trim is over 100%, it means the ecu is adding fuel to get the O2 sensor to read 14.7 A/f ratio. When the trim is under 100% the ecu is taking fuel away.

 

[JayRolla]

Yeap, you need to take out more fuel for the injectors your running. Get the lo trim too 0-5% positive.

 

[dsm-onster]

Hightrims being low mean that the injector is bigger than youve dialed it in for. Lowtrims being higher than hightrims mean that the deadtime is more than what the computer thinks. If the lowtrim were low like the high trim I would say that you just have to remove fuel through out (or change the base settings for injector size). You use the high trim to determine if your injector flow is correct. And you use the DIFFERENCE between the lowe trim and high trim to determine if you're having a deadtime issue.

So in your case assuming you have a MAFT for your 3" gm maf, you need to readjust to a larger injector setting. And then you need to remove idle fuel with the idle knob. You'll never get it perfect.

 

[nestamon99]

Thank you for the information guys. I actually have a 3.5" GM MAS