Can't change Fuel trim please help

[b15turbo]

OK im trying to tune my car and im starting from step one is to try to change my fuel trims. I have a Eprom/ecu stage 3 key drive w/550 compensation supra fuel pump and SX adj, fuel press, 550cc and safc, and the dataloger. I cannot get my fuel trims to change low, mid and HI, I tried everything from -20 to +20 and letting it idle for a while but the fuel trims still wont change, i can add fuel and take it out but fuel trims still stays the same,. LO-139% mid-139% HI-107% please help...

 

[ChvyKc]

OK im trying to tune my car and im starting from step one is to try to change my fuel trims. I have a Eprom/ecu stage 3 key drive w/550 compensation supra fuel pump and SX adj, fuel press, 550cc and safc, and the dataloger. I cannot get my fuel trims to change low, mid and HI, I tried everything from -20 to +20 and letting it idle for a while but the fuel trims still wont change, i can add fuel and take it out but fuel trims still stays the same,. LO-139% mid-139% HI-107% please help...

I actually had the same problem with my logger. I could make the fuel trims go up by adding fuel but couldn't get them to go down. I just sent you a PM by the way.

 

[oddrob]

Did you try driving around for 20 min. or so to let the comp relearn?

 

[b15turbo]

not for 20 min, i tried just let it idle for about 5 min and then i drove for a little but not 20min, I was told it should take couple of min not 20min. Does it really take that long ?

 

[Littlebeeper]

It does take that long. I'm andusting my MAFT as i installed it like 1 month ago but i live in a small town and it takes like 5-10 minutes to get anywhere. My trims will not budge unless i drive around doing errands. Sometimes it takes a week for me to have enough things to do to drive more than 10 minutes. After they start adjusting i can actually see the low trim move as i'm stopped at a red light. mid tekes longer to adjust and high is harder as you have to be driving fast

 

[steve]

First, reset your SAFC back to 0 corrections. Reset the ECU by disconnecting the power.
When you start the car again, watch the datalogger. When the COOL (ECT) is > 86F the ECU should enter closed loop and you should see the O2 voltage cycle along with the FTO2.
Once the COOL >186F the fuel trims should starts to change based on the FTO2 and the current airflow range. So at idle the FTRL should be move to cause the FTO2 to center around 100%

If the car never enters closed loop or never fully warms up the trims won't update.

Steve

 

[ChvyKc]

First, reset your SAFC back to 0 corrections. Reset the ECU by disconnecting the power.
When you start the car again, watch the datalogger. When the COOL (ECT) is > 86F the ECU should enter closed loop and you should see the O2 voltage cycle along with the FTO2.
Once the COOL >186F the fuel trims should starts to change based on the FTO2 and the current airflow range. So at idle the FTRL should be move to cause the FTO2 to center around 100%

If the car never enters closed loop or never fully warms up the trims won't update.

Steve

Tim (b15turbo) just came over to my house to see if I could figure out what is going on with the car and something is definately not right but it is beyond my knowledge. If you have the AFC zero'd out all the way across the logger shows no knock but O2 voltage is at .80 which is really lean. I know that if my car was running that lean I would have a knock count over 60 for sure.

I tried richening up the top end and the O2 voltages went down like the car was running leaner and it showed a knock count of 5 which is still not bad and it was just in one spot in the RPM range.

You have ideas steve? Is the O2 sensor shot? Is the AFC not installed right or not working properly? The one thing that I did see was that his base fuel pressure was at 30 psi at idle and I know that is to low, could this cause this problem? I am stumped on this one.

 

[b15turbo]

David, I just got home and tried to raise the fuel pressure and it will still co the same thing the car will run lean, so anyway i add fuel it starts to run lean......... so i goes the safc is wired right.

 

[steve]

It should be pretty easy to see on the datalogger if the MAF HZ changes the right amount/direction as you change the SAFC settings.

I can't guess about the rest, not enough to go on. If the O2 sensor isn't less than a couple of years old I'd replace it. Same for the fuel filter.

If you can get access to a wideband to check your results that would help make sure your not chasing ghosts.

Steve

 

[ChvyKc]

It should be pretty easy to see on the datalogger if the MAF HZ changes the right amount/direction as you change the SAFC settings.

I can't guess about the rest, not enough to go on. If the O2 sensor isn't less than a couple of years old I'd replace it. Same for the fuel filter.

If you can get access to a wideband to check your results that would help make sure your not chasing ghosts.

Steve

Can you tune according to the Hz that the datalogger is reading? I never thought to check that but I guess that would make the decision of whether the O2 sensor or the AFC was bad/not working.

My next investment will be a wideband because I always hated using a logger. Messing with MMCD while you are trying to drive is just rediculous.

 

[b15turbo]

After work today im going to get a new o2 sen. so we will se if that helps,I just dont get it, even adding fuel from the fuel press. reg. still runs lean the car just hates fuel.

 

[steve]

Can you tune according to the Hz that the datalogger is reading?

I wouldn't call it tuning. You can do quite a bit of troubleshooting with the datalogger.

Steve