Fuel trims gone crazy

[power=dsm]

I can't get my fuel trims right? All 3 of them are always out of whack. I can get the low and medium to 95% but the high is always at 121 which is soo rich. But i drive the car around for a bit and then i check them again and they all go back to 121 on all 3 of them

 

[Newlogics]

I can't get my fuel trims right? All 3 of them are always out of whack. I can get the low and medium to 95% but the high is always at 121 which is soo rich. But i drive the car around for a bit and then i check them again and they all go back to 121 on all 3 of them

Having fuel trim at 121 shows that it's lean, and ECU is trying to add more fuel. If it seems like car is running too rich still, then I would blame O2 sensor, as it is used by ECU to determine those fuel trims.

 

[power=dsm]

ok so anything over 100 means i'm to lean and the computer is trying to add fuel??

I checked my logs and my car isn't knocking when i'm just cruising around? Can i leave it like that to get better gas milage

 

[Newlogics]

ok so anything over 100 means i'm to lean and the computer is trying to add fuel??

I checked my logs and my car isn't knocking when i'm just cruising around? Can i leave it like that to get better gas milage

You shouldn't leave it like that. Your trimms are maxed out, which means there is no more room to wiggle. If something should obstract your fuel delivery or you get a bad batch of gas, your ECU can no longer richen up the mixture. You need to get down to the cause and fix it.

 

[spyderturbo007]

ok so anything over 100 means i'm to lean and the computer is trying to add fuel??

Correct, perfect trims for a 1g are 100% across the board (for a 2g it's 0%)

100% means that the O2 sensor is showing a stoichometric AFR. Anything above 100% is lean and show how much extra fuel the ECU is injecting to correct the lean condition. Anything below 100% show how much fuel is being removed.

Like Newlogics suggested, I would look into the O2. That is what the ECU uses to calculate the FT's. How old is your O2?

 

[power=dsm]

1 year old