STFT will not move

[StyleElements]

Well my attempts to tune my car with a safc and pocket logger are not working to well. no matter where I set the SAFC, be at -20% to +20% my STFT stays at 5, no matter what rpm (I let the car idle for 5 minutes before changing the SAFC) From what I can gather, this is not normal, is it? i have read and read and every document says the STFT should change easy. I have a Venom fuel pump, 550s AFPR, if i can not get this fuel trim to move would it be all right the just drive the car -10% across the board for lo and hi settings? and is 0% setting it back to factory? I dont know, tell me if im doing somthing wrong, because i can not get this trim to move. Thanks guys

 

[spyderturbo007]

My STFT changes within seconds of adjusting the SAFC-II. The LTFT changes within 60s. There is definately something wrong with your setup. Baseline for 550's should be about -18 on both the hi and low maps. Where do you have your hi and lo trigger points set? Also, did you check your installation. Almost sounds like the SAFC isn't intercepting the airflow signal. You should see a huge difference in the FT's from -20% to +20%. Did you cut the airflow signal or just splice into it. Did you arrange the two grounds properly (one needs to be closer the the ECU than the other.

I am leaning towards a wiring problem because it seems as though the SAFC isn't changing anything.

0% is the setting from the factory for the SAFC.

Also, what is your LTFT at idle?

 

[StyleElements]

My STFT changes within seconds of adjusting the SAFC-II. The LTFT changes within 60s. There is definately something wrong with your setup. Baseline for 550's should be about -18 on both the hi and low maps. Where do you have your hi and lo trigger points set? Also, did you check your installation. Almost sounds like the SAFC isn't intercepting the airflow signal. You should see a huge difference in the FT's from -20% to +20%. Did you cut the airflow signal or just splice into it. Did you arrange the two grounds properly (one needs to be closer the the ECU than the other.

I am leaning towards a wiring problem because it seems as though the SAFC isn't changing anything.

0% is the setting from the factory for the SAFC.

Also, what is your LTFT at idle?

well the safc is installed correctly, the car was dyno'd with it a few years ago, on the low settings i can pull fuel right out of it and stal the car if i want to. when i drive the car, the STFT will either always be at 5 or 17. will not change at all. my LTFT will not change from 12 no matter what. ill have a wideband in the car tomorrow, i guess im going to just tune for A/F ratios and just forget about fuel trims. the car does not ever drive any differant be at 5 or 17 so oh well i guess

 

[StyleElements]

okay my stft is either 5 or 17. idling or driving. thats it. my ltft has never onced moved from 12. so, for the stft if you average 5 and 17 thats 12 for the ltft. why 5 and 17, and why wont they move for nothing

 

[spyderturbo007]

This is a new one for me, but there are some things we can try.

If you pull off the negative terminal from the battery and allow the ECU to reset to factory defaults, upon startup both of the FT's should be at 0.

I am not really sure as to why they won't move. If they we fluctuating but remaining high, I would lean towards a dying O2 sensor.

Just for fun, take a look at your coolant temp, and the intake air temp at idle. Just to make sure those sensors are functioning.

The main reason to adjust the FT's are so that you have the maximum adjustment range on the SAFC (-50% to +50%). If your FT's are off by 12, your adjustment range on the SAFC will be off by about 3%, no big deal here.

Just a couple of things to check

 

[StyleElements]

This is a new one for me, but there are some things we can try.

If you pull off the negative terminal from the battery and allow the ECU to reset to factory defaults, upon startup both of the FT's should be at 0.

I am not really sure as to why they won't move. If they we fluctuating but remaining high, I would lean towards a dying O2 sensor.

Just for fun, take a look at your coolant temp, and the intake air temp at idle. Just to make sure those sensors are functioning.

The main reason to adjust the FT's are so that you have the maximum adjustment range on the SAFC (-50% to +50%). If your FT's are off by 12, your adjustment range on the SAFC will be off by about 3%, no big deal here.

Just a couple of things to check

well i hooked a wideband up to the car last night to see what is really going on, but of course the wideband o2 is shot, and just gives me a ERR on the display. that set me back huge. you say this could be a dying o2 sensor, well that may make sense, seeing how at wot my o2v will only peak at .17. can you explain to me what exactly fuel trims are? i mean i guess i have a good idea, but are they totally coneccted to what your a/f ratio is?

so if my STFT is at 17, this would just be telling me im lean because the ecu is trying to correct the lean condition? so if i have positive fuel trims then the wideband is not going to say rich no matter what? if this is true, can i just forget about fuel trims and just tune with the wideband seeing how thats telling me stright up how it really is? thanks a lot

 

[spyderturbo007]

Sorry to hear abou the WB

If your O2 max votage at WOT is 0.17 then it sounds like you need a new O2 sensor. Just bite the bullet and get one from the dealer (about $100). I would recommend against an aftermarket sensor, as most are only 2 wire and don't have heaters.

FT's are the ECU's way to adjust for a rich/lean condition. It looks at the O2 voltage (for the most part) and then decides if the mixture is rich or lean. 0.50 is the stoichometric point that the ECU is shooting for. It is normal for the O2 voltage to fluctuate above and below 0.50v (helps with the efficiency of the cat). If the ECU sees that the O2 voltage is below 0.50 more often, it then decides that you have a lean mixture and adjusts the STFT in the positive, >0 direction. If this condition persists for a certain length of time, the ECU will transfer that value into the LTFT and you will see the STFT return to 0.

You are correct, if your FT's are high the ECU is compensating for a lean condition. Most of the time this is caused by a dead or dying O2 sensor. As the O2 sensor ages the voltage degrades. This is why it's a good idea to replace it every so often. In the long run it will save you money in gas .

I am not going to comment on the WB aspect of your question as I have no experience with WB's. I don't want to start spreading incorrect information

All I can say is, I have never heard of a WB used for anything other than WOT tuning.

 

[StyleElements]

Sorry to hear abou the WB

If your O2 max votage at WOT is 0.17 then it sounds like you need a new O2 sensor. Just bite the bullet and get one from the dealer (about $100). I would recommend against an aftermarket sensor, as most are only 2 wire and don't have heaters.

FT's are the ECU's way to adjust for a rich/lean condition. It looks at the O2 voltage (for the most part) and then decides if the mixture is rich or lean. 0.50 is the stoichometric point that the ECU is shooting for. It is normal for the O2 voltage to fluctuate above and below 0.50v (helps with the efficiency of the cat). If the ECU sees that the O2 voltage is below 0.50 more often, it then decides that you have a lean mixture and adjusts the STFT in the positive, >0 direction. If this condition persists for a certain length of time, the ECU will transfer that value into the LTFT and you will see the STFT return to 0.

You are correct, if your FT's are high the ECU is compensating for a lean condition. Most of the time this is caused by a dead or dying O2 sensor. As the O2 sensor ages the voltage degrades. This is why it's a good idea to replace it every so often. In the long run it will save you money in gas .

I am not going to comment on the WB aspect of your question as I have no experience with WB's. I don't want to start spreading incorrect information

All I can say is, I have never heard of a WB used for anything other than WOT tuning.

well .. what i dont understand is this o2 sensor is not very old. it prolly only has 5,000 miles on it, its prolly 2 years old, if that. i checked price at autozone the other day and it was actually only 50$ for the factory sensor. but i dont know, everything is pointing to a bad sensor, between .00 - .17 at wot and stuck fuel trims. i just hate to buy one if its not really bad with no money to spare.

just cruising, and getting in the gas a little, i have see my o2v hit .5, but nothing above that, and wot it drops around .1. being new to tuning myself it sucks i have this BS problems. i appreciate your help

 

[spyderturbo007]

Did you take a look at the coolant & intake air temperature on the logger when the car was warmed up? If they look normal, the only thing I can come up with is the O2 sensor.

Maybe one of the other guys has another idea.