Injuneer

There' s a flag called "Fuel Trim Enabled". I don't see that in the log. Is it available data, but not included in the log?

It's possible that is an indication of why fuel trims are not being learned/used. I have no idea what triggers that flag, other than it is always "0" (inoperable) in open loop, goes to "1" (operable) in closed loop, and goes to "0" in PE mode..... all of which is logical. But there may be some other parameter that also affects the flag. GaryDougs scan programs all include this flag.

Typically when Fuel Trim is not enabled, the PCM uses the learned (stored) LT's, and locks the ST's at 0. Did you clear the PCM before data log 1, because that would explain all 0's for the LT's? But if the LT's are enabled, even though they have been cleared to "0" they should start to readjust immediately in closed loop. What is really weird is that the ST's on Bank 1 are not working, but the ST's on Bank 2 are working for 36 seconds at the beginning of the "no trim" log. And of course the fact that LT's and ST's intermittently turn on for a couple seconds at random times..

Absolutely have never observed this before in reviewing hundreds of data logs from various sources. And I do not have knowledge of all the intricacies of the PCM's inner workings. But you are saying Solomon has seen this and has no explanation?

slikrider20

I honestly have not seen that available in any of the options in ECM PRO, and it doesn't let me add custom PIDS. I did find a custom pid (22110A) that I could enter into torque pro that is called "Fuel Trim Learn" and has a value of 0-1 so that is probably it. I'll test that out.

I didn't clear the PCM after log one. I simply restarted the car.

Solomon says he has seen this before, and that it seems random. It's happening more consistently to me than it ever has before.. He said Tunercat has no idea either. I wonder if more people have the problem just aren't aware of it? Almost every time I drive my Camaro I have my laptop in there logging/viewing stuff.

About to hop in my car now...we'll see if the trims are there and/or that custom pid for Fuel Trim Learn works.

Injuneer

“Fuel Trim Enabled” is not likely the same as “Fuel Trim Lean”.

JakeRobb

Fuel Trim Learn, however, seems likely to be the same I think?

Injuneer

OK. I read it too fast the first time.

slikrider20

Yeah It says "Learn" not "lean".

And sure as stuff, when I started my car today, the trims were working great and the car was pulling hard as could be.

Stopped at Walgreens for 5 minutes, restarted the car and poof go the trims and my power.

I guess I can only drive it once a few days and not restart it?!

Injuneer

I've scrolled through the "no FT" file looking for something that could possibly be triggering the FT's to turn on and off, but it looks very random. As I noted, in looking at hundreds of LT1 data logs over a period of 20 years, I have NEVER seen this before. If Solomon has seen it before, it may be something inherent in his tunes. That's the best I can come up with.

There are other strange things happening. It's idling in Cell 16, you open the throttle, and it stays in 16 for a while. In the "FT" file, it's idling in Cell 16, you tweak the throttle, and is stays in Cell 16, but the LT1 changes from -10.9% to -2.9%. Seems like it actually changed cells, but it doesn't indicate the new cell identification. Generally, you open the throttle and the PCM figures it's not idling any more, and switches rapidly to the appropriate cell. Cells are defined by RPM and MAP, but there is no correlation of MAP to the FT's turning on and off. It's running in Cell 0 (not a Cell you often see) when MAP is as high as 50 kPA, but the upper limit for Cell 0 in stock programming is 30 kPa and 900 RPM max. Maybe he changed the cell limits. Part of the difficulty with interpreting the log is the slow scan rate.

slikrider20

The cell limits have definitely been changed.

That's a good observation that something in his tunes could be causing this... And the fact that it does it in both of the pcms I have. I wonder if the cell limits are confusing the PCM? I'll tweak them back to stock and see what happens.

The slow scan rate probably has something to do with how many parameters are being logged. Are there any not useful ones I have on there that could be deleted?

Injuneer

Has he ever installed a "BLM locker" (BLM = LTFT)? Sometimes that is done to prevent the LTFT's from changing, once all the parameters have been tweaked to get the LTFT's to 0.

I don't know the limits of the software you are using. GaryDoug's Scan9495 software logs 59 columns at 8+ frames per second. It has things that are related to Fuel Trim Enabled, like "O2's Ready", etc.

slikrider20

I have a 96, therefore I'm obd2. Don't think his software would work? The blm locker patch only worked on obd1 cars as far as I knew. (tried it in tuner pro)

Honestly I tried the scan9495 software when I converted to obd1 and wasn't a fan.

I might look into more logging options or investigate why the data is slow. Could be my laptop as well.

ACE1252

I think it's the OBDII pcm or the way the pid commands are being pulled from it. With Scan9495 on an OBDI PCM, it gets some crazy fast pid update rates compared to my OBDII setup. I've got Autotap and Scan XL Pro. Autotap is faster than Scan XL Pro....but not by too much....neither can come close to the OBDI pid update rate.

I asked about your software as I know Autotap is not reporting the bank 2 long terms correctly.

Injuneer

There is an OBD-2 version of Gary's program. But if you don't like Scan9495, you probably won't be happy. You're the first person I've heard that didn't like it.

slikrider20

Just reading on Stevo's website and he mentions how the CCP system is somehow tied to BLMS.

Charcoal Canister Purge (EVAP) ? fbodytech

Wondering if this might shed any light for anyone? Just looking through Solomon's tune in JET and it doesn't look like he touched any of the CCP stuff.

Also, just throwing this out there, but i've noticed that my car has to sit for at least 6 hours to get the trims to show back up, but it's only the short trims. The long trims seem to still show up all the time.

slikrider20

Here's an easier log file to try and diagnose this problem. This is off a PCM reset, so the long trims don't show up right away. I let the car sit all day, and go to fire it up tonight. It runs great, trims work good, positive and negative, etc. I restart the car around frame 1000, it goes back to open loop for a bit, and then as soon as it enters closed loop the negative trims disappear. Meanwhile, the car feels sluggish, doesn't sound the same, etc.

I tried to organize/manage the log a bit so it's easier to see.

Injuneer

It is screwed up the entire data log.

Yes, for the first 1,000 frames you have short term fuel trims (although there are periods where they cut out, mostly on decel in Cell 3). The problem is, you have very few instances where LTFT's are anything other than 0%, and when they do show up as something other than 0%, they move all over the place, generally associated with decel.. There and a couple random places, they hang at 0%. There are extended periods where the short terms are pulling out up to 15-18% of the fuel. The long terms should start going negative until the short terms return to 0%. But they don't, they just stay at 0%. Also seems to spend an irrational amount of time in Cell 3, including decel, but I have no idea where the cell boundaries have been changed to. Never see Cells 17 or 18, and that too is unusual.

In the later section, after it re-enters closed loop at frame 1053, the short terms are turning on and off, and the long terms are turning on and off. But even though cells change, the LTFT's seem to be the same numbers in many cases, or change suddenly at random, even though there are no STFT's to drive the change. But to say the STFT's disappear is not correct. You have to scroll through the entire 2.200+ frames to truly see what s going on. And that is hat occupied the last hour+ of my life.

Conclusion at this point is either the program, the PCM (unlikely) or the scan software is screwed up. There is no point to keep looking at these logs, because I cannot correlate the STFT's and LTFT's turning on and off at random to any other parameter in the logs.