Idle Learn Problem

[RevGTO]

After I installed my ported throttle body and did my CAI I had "cruise control" and hanging idle problems. After daily driving for about six weeks it went away. When I did a full reflash to an 02 OS, the problem recurred, but again, it went away after about six weeks.

Today I did a calibration only reflash (tranny tuning) and surprisingly, it's back. I don't want to deal with six weeks of this annoying behavior every time I change a few calibrations. Any suggestions? Would doing an "idle relearn" help? How is it done?

[RevGTO]

Found the answer on LS1tech. I'll try the idle relearn procedure, and if it works, I guess I'll have to do it each time I reflash.

[TAQuickness]

It sounds like B4307 may be off a bit and that it's taking your PCM 6 weeks to re-learn it's idle. Take a look in the tutorials section at the idle sticky.

[SSpdDmon]

Was the throttle body epoxied? If so, that would be my first guess as to the cause of your problem.

[RevGTO]

No epoxy. Hole wasn't drilled out either. I think I'm getting some air bleed past the blade, because my IAC's typically are at zero at warm idle. So my PCM has to work overtime to get things right, but once it sorts out, it all works perfectly.

[jfpilla]

No epoxy. Hole wasn't drilled out either. I think I'm getting some air bleed past the blade, because my IAC's typically are at zero at warm idle. So my PCM has to work overtime to get things right, but once it sorts out, it all works perfectly.

If the throttle bore was touched when porting it could be the problem. Your airflow tables would be out of sinc and in need of tuning. It's not too easy if the porting job is at fault. The good news is you car is learning and compensating so it can be done. You might start with B4307,B4309 and B4318 and maybe those tables will be enough to get close enough so that learning is not so long a time frame. As was pointed out there are plenty of writeups on transition tuning.

[RevGTO]

I appreciate all the references to the tables, etc. I'm familiar with them and what they do, but am unsure of how to go about adjusting them for my scenario. I've looked at the write-ups but don't get a clear sense from them of how to approach the problem.

I did a log today and it appears to me that the PCM is commanding more IAC than is needed. If anyone would like to look at the log and advise me, that might help.

[SSpdDmon]

Desired Idle Airflow is the table that commands the IAC. You need to log your STIT's, LTIT's, and the calc'd RAF pids to figure out how much to pull out of that table. Once you have the PCM squared away, then you can work on IAC counts with the throttle body set screw.

[RevGTO]

Thanks for the help. ST/LTIT = ST/LTFT, fuel trims? If so, I logged those. Do you need to set up a MAP to log RAFIG/PN? I selected those PIDs but I don't think it worked ... RAFIG was zero or negative most of the time. If so, can you give me the row/column/data to set it up. Thanks again for the guidance.

[SSpdDmon]

STIT = Short Term Idle Trims (not fuel trims)

GM.IAC_LTD_DMA = LTIT In Gear A/C Off
GM.IAC_STD_DMA = STIT In Gear A/C Off
CALC.RAFIG = LTIT + STIT for In Gear

They are found under the Idle section in the logged .pids tab [F8].

You make the map look like the Desired Idle Airflow table with 1 column and several rows for each ECT temp:

You highlight the entire table in the tuning software, right click, and select copy with labels. Then, when you go to make the map, you hit the paste with labels button on the rows tab and select the ECT pid. The way I create the single column is to reference it to RPMs and use the label ",8000" (yes, use the comma). The RAFIG is the data.

Add the results to the Desired Idle Airflow Table in the tune.

[RevGTO]

Thanks a lot! Very helpful. Should I save the RAFIG map in the map or the pid folder?

[SSpdDmon]

MAP folder if you want to use it again.

[RevGTO]

It prompted the pid folder, so that's where I saved it, but I can move it. So with the RAFIG pid selected, Flashscan will reference that map for the calculated data even if it's not in the pid folder?

[SSpdDmon]

It doesn't really matter where you keep it I don't think. I was only suggesting keeping it with all of the other maps to prevent you from having to search through multiple folders to open it the next time you want to use it. :)

[RevGTO]

Update: Well, I did log RAFIG and my results average out at -.42 to -.17. Do I take the average number for each temperature row and subtract (since they are negative) that figure from the Desired Airflow setting? In some cases, it is close to 20%, and that seems like a lot. Also, I want to be sure if you use the minimum, maximum, or average number - thanks.

[SSpdDmon]

You use the average numbers. But once I'm within -0.5~0.5 grams/second for each cell, I call it a day. The idle trims should be able to compensate for that much. It's never going to be perfect.

[RevGTO]

I logged lbs./min, so the swing is much more considerable. Plus the overall reduction in aiflow called for is substantial - like I said, in some cells, 20% or more. It seems like a lot and makes me wonder if it could be right or if I'm making a mistake somewhere.

[SSpdDmon]

It's based on what the idle trims are doing already in the PCM. You're logging the changes the PCM has made to obtain the right idle airflow. If you feel the changes are too aggressive, then apply only half of the correction and smooth out the curve. Then, give it another go the next day when it has cooled off. As a reference, I know my h/c M6 likes .86~.80 lbs/min at idle (ECT>176*F).

[RevGTO]

Thanks. I logged some more today and it is settling in at -.17 correction from 60* to 212*F. I may subtract that amount from all the cells and see what happens. My concern is that that brings the operating temp cells down to .65, but I can always bring it up if it seems to run funky.