'7060 data log analysis - help requested!

Starting another thread on one of the most significant lingering tuning issues on my vortec/TBI 383 for my '91 3/4T 4wd Burb with 4L80e and 7060 PCM. This thread is essentially the continuation of another (here) but I thought I'd start fresh since I've done some things since then and have started zeroing in (I hope) on the problem.

Lingering issue: weird and annoying cyclic surge on deceleration. Instead of RPM decreasing linearly during smooth decel, it oscillates with a 200-300 rpm amplitude and approx 1 sec period.

What I've done: installed AEM WBO2 system. '7060 does not have provisions for incorporating WB data with its datastream, but I can see it pegging lean during decel in cycles that match those described above.

I've also gotten better with tunerPro datalogging and I have exported a recent datalog to an Excel file that has a number of decel events included. Then I grabbed the data from just one of those events and pasted it into another sheet in the same file. Then I graphed RPM vs Time on one vertical axis and Speed vs time on the other vertical axis. The graph shows speed decreasing smoothly (it's in small steps due to TP only reporting speed to nearest MPH) while RPM looks like a decreasing sine wave.

I tried to attach my Excel to this post, but the site wouldn't let me. Here's a link to it shared on Google Drive. If someone was willing to look on at my log, but doesn't want to click the link, PM me and I'll get it to you any way you want.

What I'm asking for: help with figuring out what is causing the ECM to pull fuel in a cyclic fashion during decel. In the export I've included everything that I thought would remotely matter in trying to figure this out, but if I've missed something let me know and I'll gladly redo the export. My only clue right now is the parameter called "AIR Management" My burb did not come stock with an AIR pump and it certainly does not have one now, but I'm wondering if this could be doing something to cause problems. It does seem to trigger ON and OFF seemingly at random, but it also seems to doing it at other times besides just decel. Maybe something else completely, I don't know. Just know I'm at my wits end to try to get the decel surging eliminating. There are a couple other lingering problems but I'll tackle those next.

One other clue, I can eliminate the surge completely by running open loop.

Any thoughts? Anyone?

Quote:

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Originally Posted by Daveo91

Starting another thread on one of the most significant lingering tuning issues on my vortec/TBI 383 for my '91 3/4T 4wd Burb with 4L80e and 7060 PCM. This thread is essentially the continuation of another (here) but I thought I'd start fresh since I've done some things since then and have started zeroing in (I hope) on the problem.

Lingering issue: weird and annoying cyclic surge on deceleration. Instead of RPM decreasing linearly during smooth decel, it oscillates with a 200-300 rpm amplitude and approx 1 sec period.

What I've done: installed AEM WBO2 system. '7060 does not have provisions for incorporating WB data with its datastream, but I can see it pegging lean during decel in cycles that match those described above.

I've also gotten better with tunerPro datalogging and I have exported a recent datalog to an Excel file that has a number of decel events included. Then I grabbed the data from just one of those events and pasted it into another sheet in the same file. Then I graphed RPM vs Time on one vertical axis and Speed vs time on the other vertical axis. The graph shows speed decreasing smoothly (it's in small steps due to TP only reporting speed to nearest MPH) while RPM looks like a decreasing sine wave.

I tried to attach my Excel to this post, but the site wouldn't let me. Here's a link to it shared on Google Drive. If someone was willing to look on at my log, but doesn't want to click the link, PM me and I'll get it to you any way you want.

What I'm asking for: help with figuring out what is causing the ECM to pull fuel in a cyclic fashion during decel. In the export I've included everything that I thought would remotely matter in trying to figure this out, but if I've missed something let me know and I'll gladly redo the export. My only clue right now is the parameter called "AIR Management" My burb did not come stock with an AIR pump and it certainly does not have one now, but I'm wondering if this could be doing something to cause problems. It does seem to trigger ON and OFF seemingly at random, but it also seems to doing it at other times besides just decel. Maybe something else completely, I don't know. Just know I'm at my wits end to try to get the decel surging eliminating. There are a couple other lingering problems but I'll tackle those next.

One other clue, I can eliminate the surge completely by running open loop.

Any thoughts? Anyone?

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Adding .zip Excel file.

dave w

Thanks @Dave w for posting the .zip of my excel file.

Anyone have any thoughts about my cyclic decel surge issue? Something is causing it to drastically pull fuel and then turn it back on in a periodic fashion. NOTHING I have done to the tune has changed this, other than keeping it out of closed loop.

Alternatively, any thoughts of a mitigation for the problem or work around? I'd rather not always run open loop but am considering it. If there was someway to force it to OL during decel and idle only I think it would solve it, but I'm not aware of any way to do that. I'm also going to try some more drastic DFCO settings to cover more decel events and see if that changes anything. The weird thing is it doesn't seem like DFCO is ever triggering according to my logs so I guess that's where I need to focus. The AIR MANAGEMENT flag I mentioned previously is also something I want to focus on -- it seems like it should be easy to test by turning it off in my BIN, but there's nothing about that parameter at all in my .xdf or it is called something else.