LTFT Response Time

[vettenuts]

How long does it take to update a LTFT? I have an issue with code P0172 and subsequently found an intake leak. I am still getting the code on occasion and am trying to figure out if the time it takes to update the LTFT is such that the code is still setting while the trims are being updated by the PCM.

[Redline Motorsports]

What year and what model are we talking about?

[ringram]

Just reset the codes and trims. Then if it comes back you know its still happening.

[vettenuts]

Just reset the codes and trims. Then if it comes back you know its still happening.

While I have considered that, watching the error occur has given me an opportunity to monitor it. While driving yesterday, I found that a certain driving condition would set the error and I could do a reset on the fly through the DIC and I found that after several minutes the error apparently didn't come back for that particular driving condition. I am trying to figure out if this amount of time is required for the LTFT's to move. According to Probst's book, it takes about 10 minutes. If that is the case, I may be OK.

[SSpdDmon]

If you hold a constant rpm/load on the motor, the LTFT should update in about a minute. For example, when the evap system kicks in after filling my tank, my LTFT's drop to -9 to -11 within the first minute of driving at a given load/rpm. It also has to do with STFT switching frequency. At idle and low airflow scenarios where your STFT's aren't switching as fast, it will take longer to update your LTFT's.

I'd say keep checking for upstream leaks. But if you can't find any, look to the O2's. That bank may be going bad causing the PCM to flood that side of the motor. Although in that case, it would be doing it across the board (all driving rpms/loads).

**Also, keep in mind positive fuel trims under low airflow scenarios tend to indicate downstream/exhaust leaks.

[vettenuts]

I had an earlier exhaust leak behind the O2 (just behind it) and my tuner thought this might have done in the O2, haven't got to that yet. Also, what affect does ambient temperature have on the fueling? Yesterday was a particularly hot day.

[wait4me]

b4113 will make the strims faster which will in turn make your ltrims update faster if needed

[vettenuts]

I logged some data tonight . I am going to start a new thread with the findings so far.