Crazy high LTFT, lean codes, e85...

[steve99]

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.

you would expect positive due air leak in exhaust as @phrosty said ltft can vary at idle due big changes in iat from stuck idling in traffic to mo.ving, variation of 4% or so not unusual, if its like 10% variation then suspect something.

[gonzo]

Originally Posted by phrosty

A dud battery would not cause high fuel trims.

Then why did it for me? My fuel trims were high, IAM wouldn't stay at one, and multiple codes kept popping up. About two days later my car wouldn't start. Changed the battery and everything went back to normal.

[D_Thissen]

Originally Posted by gonzo

Then why did it for me? My fuel trims were high, IAM wouldn't stay at one, and multiple codes kept popping up. About two days later my car wouldn't start. Changed the battery and everything went back to normal.

Might be a combination of things. Car might have learned new higher fuel(If I am not mistaken, a +LTFT means the car is running lean and more fuel is being added) trims over time, which might have led to it being difficult to start. So now you crank and cranks, and the battery dies. Replaced the battery and now the fuel trims go back to what the tune has stored (ecu reset?). The OEM batteries are small and it wouldn't take much to deplete them to the point where it wouldn't start.



PS: What codes were you getting??

[cameronjones239]

Check your breather tube that connects to the intake just in case, that will cause ltft to jump around quite a bit.

[steve99]

Originally Posted by gonzo

Then why did it for me? My fuel trims were high, IAM wouldn't stay at one, and multiple codes kept popping up. About two days later my car wouldn't start. Changed the battery and everything went back to normal.

Yes dying battery, bad battery connection or bad earth connection bad alternator\voltage regulator ect can cause very weird issues on cars full if electronics. ECU needs stable voltage reference to accuratly interpret sensor voltages.
Batterys act a large capacitor to smooth voltage fluctuations\spikes noise ect.