How do you reset fuel trims? I've had this issue of my fuel trims always being .1 (.1008 on the evoscan screen). It doesn't matter how many times I reset the ecu (disconnecting battery) or what STFT is doing it's always .1. Even today after my 1000cc injector install. I have Evoscan 2.6 currently, but it was the same for 2.5 and probably whatever I had before that. I've even swapped intakes (reset ecu) and it doesn't change. I've tried the "Fuel trim idle/Fuel trim cruise" codes in Evoscan too. Same thing.

Any ideas?

Thanks.

 

That is the ECU default when its reset/reflashed.

 

So how long do they take to "set"?

 

If you have Tephra's ROM with disabled rear O2 or you disabled rear O2 via periphery, this may happen. If you have done that — enable rear O2 and see if the trims start working again.

 

The rear o2 sensor shouldn't affect fuel trims.

 

Depends how often you drive the car and the circumstances. The fastest way for them to adjust is to cruise at a steady speed/load for extended periods.

 

Alright, looking though my logs after the injector install, I think I can see where the low and mid ltfts were set, but they set to .1. In the log, there is nothing for low/mid ltft, then all of a sudden there's .1.



This is the trims setting right?

 

I do have the rear o2 disabled. I'll will try that, although, like S2kracka, I didn't think the rear o2 mattered. But, now that I think about it, I noticed this around the same time that I disabled it.

 

Of course it doesn't. At the same time disabling the rear O2 affects ECU in a way that it stops recording trims. I've mentioned it before somewhere i think...

 

I see. Thanks everybody for the help. I've enabled the rear o2 and will continue the injector tuning tomorrow.

 

.....

 

Did you ever get this issue resolved if so what did you do? have the same problem.

 

The "0.1008" value is because the exact decimal value is not in the EvoScan fuel trim formula. The following EvoScan entries will give you zero values for the fuel trims when they really are zero:

<DataListItem DataLog="N" Color="" Display="LT Fuel Trim Low" LogReference="LTFT_Low" RequestID="0C" Eval="0.1953125*x-25" Unit="%" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="-13" GaugeMax="13" ChartMin="-13" ChartMax="13" ScalingFactor="1" Notes="" Priority="1" Visible="false" />
<DataListItem DataLog="N" Color="" Display="LT Fuel Trim Mid" LogReference="LTFT_Mid" RequestID="0D" Eval="0.1953125*x-25" Unit="%" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="-13" GaugeMax="13" ChartMin="-13" ChartMax="13" ScalingFactor="1" Notes="" Priority="1" Visible="false" />
<DataListItem DataLog="N" Color="" Display="ST Fuel Trim" LogReference="STFT" RequestID="0F" Eval="0.1953125*x-25" Unit="%" MetricEval="" MetricUnit="" ResponseBytes="1" GaugeMin="-25" GaugeMax="25" ChartMin="0" ChartMax="200" ScalingFactor="1" Notes="" Priority="1" Visible="False" />

 

I had the rear o2 check disabled via ecuflash and Tephramod 5.1. I just went into ecuflash and enabled it. It works just fine now. The rear o2 cel returned, but once I get off my lazy azz, i will disable it again. Which makes me wonder, if I disable it and the ecu no longer records trims, is it going to affect my tuning any?

 

Which periphery bit did you have disabled to stop the rear O2 CEL?