Crazy high LTFT, lean codes, e85...

[nickw14]

Hey guys. So I am running the OFT e85 tune for the stock fuel system. My LTFT has always been somewhat high, but it usually stays below 20% at idle. I had a little trouble running lean at idle so I changed the AFR tables to bring the AFR down to about 13.5/14.0 (it fluctuates).

Thursday evening I was sitting in my car and the engine light and trac light came on. I checked the code and it was P0171 (lean). I started watching the AFR and it hovered around 15-15.5. But LTFT was all the way up to 38%! This does not seem right...

My first guess was that the ethanol mixes in my area changed from their winter to summer mix and the tune is just trying to account for the change in e%. Needless to say, I will probably go back to 93 for a while after this tank is empty.

[phrosty]

What do your fuel trims look like on 93?

On a healthy car, positive fuel trims of 38% would seem to indicate much higher than 85% ethanol content...

[continuecrushing]

you verified the tune on your car?

Plug in the OFT and go to tunes, and the little " * " will be next to the tune thats currently written

[nickw14]

Originally Posted by phrosty

What do your fuel trims look like on 93?

On a healthy car, positive fuel trims of 38% would seem to indicate much higher than 85% ethanol content...

I didn't pay too much attention to the fuel trims on 93.

Originally Posted by Shutter

you verified the tune on your car?

Plug in the OFT and go to tunes, and the little " * " will be next to the tune thats currently written

I am on the correct tune, yes.

[steve99]

Originally Posted by nickw14

I didn't pay too much attention to the fuel trims on 93.



I am on the correct tune, yes.

Fuel trims that high indicate

1 you running a petrol tune on E85
2. you have intake or exhaust leak
3. you have aftermarket intake that needs maf rescaled.
4. damaged o2sensor ot maf sensor.

[nickw14]

Originally Posted by steve99

Fuel trims that high indicate

1 you running a petrol tune on E85
2. you have intake or exhaust leak
3. you have aftermarket intake that needs maf rescaled.
4. damaged o2sensor ot maf sensor.

2 and 4 sound the most likely. According to the maf rescale thread, I should not rescale when using e85. I do have an aftermarket exhaust but I've had that for a few weeks now with no issues.

[steve99]

Originally Posted by nickw14

2 and 4 sound the most likely. According to the maf rescale thread, I should not rescale when using e85. I do have an aftermarket exhaust but I've had that for a few weeks now with no issues.

if the fuel trims are high at idle and low rpm and ok midrange and higher then that usually indicates leak somewhere

is your intake stock ?

[nickw14]

Originally Posted by steve99

if the fuel trims are high at idle and low rpm and ok midrange and higher then that usually indicates leak somewhere

is your intake stock ?

No, I have a k&n intake.

I will check my exhaust for leaks when I get a chance.

[steve99]

Originally Posted by nickw14

No, I have a k&n intake.

I will check my exhaust for leaks when I get a chance.

I have not scaled k&n intake so not sure how off the maf scaling is

if its the one linked below then i would say the intake is the problem, it has the maf sensor way to close to throttle body and its unlikely it has air straightner like stock intake, it likey to have bad turbulant flow arroind maf sensor throwing off maf scaling and making it difficult to scale.

i recomend you put stock intake back in and just get a drop in filter for stock intake

http://www.knfilters.com/mobile/mPro...prod=69-8619TS



if you have a look at any logs you did on petrol will tell you if maf scaling is off, i suspect the intake may be your issue.

you can scale on e85 its just more complex due changing e%.

[gonzo]

Originally Posted by nickw14

Hey guys. So I am running the OFT e85 tune for the stock fuel system. My LTFT has always been somewhat high, but it usually stays below 20% at idle. I had a little trouble running lean at idle so I changed the AFR tables to bring the AFR down to about 13.5/14.0 (it fluctuates).

Thursday evening I was sitting in my car and the engine light and trac light came on. I checked the code and it was P0171 (lean). I started watching the AFR and it hovered around 15-15.5. But LTFT was all the way up to 38%! This does not seem right...

My first guess was that the ethanol mixes in my area changed from their winter to summer mix and the tune is just trying to account for the change in e%. Needless to say, I will probably go back to 93 for a while after this tank is empty.

Originally Posted by steve99

Fuel trims that high indicate

1 you running a petrol tune on E85
2. you have intake or exhaust leak
3. you have aftermarket intake that needs maf rescaled.
4. damaged o2sensor ot maf sensor.

When I had a similar issue (lean and etc. codes, high ltft+stft, lowered iam) my car wouldnt start a few days later. Turned out it was a dead battery. Replaced it and everything went back to normal. Maybe you should add a "5. your battery is dying"

[phrosty]

Originally Posted by gonzo

When I had a similar issue (lean and etc. codes, high ltft+stft, lowered iam) my car wouldnt start a few days later. Turned out it was a dead battery. Replaced it and everything went back to normal. Maybe you should add a "5. your battery is dying"

A dud battery would not cause high fuel trims.

[aagun]

back to 93
install oem intake

reset ur rom

check ur ltft and stft


if still high then check ur DI failure coils , and replace the one or replace all ur DI . and then be sure u do not have kcfb while drive , i u do retard ur ignition map

[DarkSunrise]

Originally Posted by steve99

if the fuel trims are high at idle and low rpm and ok midrange and higher then that usually indicates leak somewhere

is your intake stock ?

Could a high negative LTFT be caused by an exhaust leak at the header? I've been seeing about -6.xx to -7.xx at idle recently. From what I understand, exhaust leaks usually cause positive LTFT's at idle (pre-02 sensor leak allows fresh air in).

I think I can hear a slight leak at light loads, but would have expected to see positive LTFT's which is why I'm perplexed.

[phrosty]

Originally Posted by DarkSunrise

Could a high negative LTFT be caused by an exhaust leak at the header? I've been seeing about -6.xx to -7.xx at idle recently. From what I understand, exhaust leaks usually cause positive LTFT's at idle (pre-02 sensor leak allows fresh air in).

I think I can hear a slight leak at light loads, but would have expected to see positive LTFT's which is why I'm perplexed.

A healthy car will see trims fluctuate somewhat at idle due to highly variable intake temps. You might not have anything to worry about.