Park idle rich, in gear at same rpm/map not

[TheApocalyptican]

I've got a strange problem with the Suburban in my signature(or at least seems strange to me, but maybe is normal)where the 800/30 cell(I think the 800/40 does too) runs down to 108blm when in park. This same cell when in gear however is tuned to, and registers when logging to be around 128. I've gotten everything dialed in, but these cells at idle in park. Biggest reason I am concerned is that I've got an emissions test coming up in early May, and here they do a parked idle, and a parked 1200 rpm test, and I'd prefer to have the fueling where it should be. So is this something that is normal, and either way, is there something I can tune to fix this?

[EagleMark]

Always do your idle at end of log after engine was warmed and driven, not at beginning when there's choke, cold intake, running Open Loop etc... it's a wet intake. You should be in different VE area in P/N then in Gear. RPM is higher in P/N, and lower in Gear. By a little in this low resolution table. Then it does not use just that cell, it interpolates a VE number from that cell and four surrounding cells, interpolation. So Smoothing the VE table helps.

There's usually 16 cells for BLM Learn and one is separate for idle, this is why you get a change sometimes.

 					;
LD2AB   FCB  11     ; Freq of blk learn update, (600 Msec) 
                    ; VAL = (N * 20)+1 
					;---------------------------------------------
					;
					;                   _______|______|_______|______
					;                          |      |       |
					;                     12   |  13  |  14   |  15    
					;                   _______|______|_______|______  HI MAP 81 Kpa
					;                          |      |       |
					;                      8   |  9   |   10  |  11     
					;                   _______|______|_______|______  MID MAP 58 Kpa
					;                          |      |       |
					;                      4   |  5   |   6   |   7     
					;                   _______|______|_______|______  LO  MAP 18 Kpa
					;                          |      |       |
					;                      0   |  1   |   2   |   3
					;                   _______|______|_______|______
					;                          |      |       |       
					;     750   LO RPM   ______|      |       |
					;                                 |       |
					;    1800   MID RPM  _____________|       |
					;                                         |
					;    2600   HI RPM   _____________________|
					;
					;---------------------------------------------

There is no BLM Cell number in $42 data to tell. After tuning I like to disconnect battery to clear the BLM Learn to see what my new adjustments are doing immediate. Then instead of seeing what's stored and waiting for INT to move enough to adjust it I see BLM raising or lowering. Do all this warmed up as well. 108 is an issue because that is as low as it will go, it's still trying to take out fuel. Don't get stuck on everything having to be a perfect 128, can't do it! Even if you could it'd be different when weather changes.

If all that fails look at "O2 - Idle AFR Bias Value" = Bias used to lower AFR at idle.

[TheApocalyptican]

108 is an issue because that is as low as it will go, it's still trying to take out fuel.

I actually never do any VE tuning without letting the truck warm up first. I usually let it warm up some in my driveway, and then take it out. Once the closed loop kicks in, I wait a little longer, and then clear the blm table to start fresh with a warmed up engine. I do realize that the in gear and park rpms are different. I'll have to do another log to be absolutely sure of the cells that are off, as I am currently thinking back to when I tuned in January. I just know, that thru several runs, I got the VE table in gear to be around 128, only to return home, and park in my driveway, and see the blm drop out to 108. It would concern me less if the number was even at 109. But as you said, 108 is as low as it will go, and thus why I think something has to be amiss.

Also, as a completely different question, but one that could be relevant here...I know it is possible to adjust the low end of the blm scale to be lower than 108. What I am wondering is, if I lower that, can the computer actually read below the 108, or is that as low as it can effectively work, and the real reason the number is adjustable is due to the fact that the same programming was used in multiple vehicles?

[EagleMark]

You could lower the BLM min, but realistically you need to pull some fuel from the idle cells.

What bin? BCC code?

You sure it's in Closed Loop when reading 128 BLM? You can post a log if you want us to take a look?

[TheApocalyptican]

You could lower the BLM min, but realistically you need to pull some fuel from the idle cells.

What bin? BCC code?

You sure it's in Closed Loop when reading 128 BLM? You can post a log if you want us to take a look?

$42 ASDU. The low blm question was more of a curiosity than anything. It's definitely in closed loop. It's not a dead on 128 just around there due to my tuning. I'll get a log posted up here soon and see what you think.

[EagleMark]

Post your bin too.