Very lean at idle RPM/MAP problem

[jnorris]

To confirm that the B3617 table truly had an affect on the cold ECT AFR I loaded PCM files with and without this table being zeroed out. With the table at stock values and zeroed out the AFR on the WB was the same. I have put this table back to stock.

I have for the most part corrected my cold ECT lean problem by putting in richer than desired values at low ECT idle MAP positions in the OLAF (B3605) table and using modified 1998 B3702 and B3703 tables. See below:

B3605 at MAP 50-55/-10c-70c
12.070636
12.070636
12.070636
12.070636
12.070636
12.524798
13.094107
13.895787
14.628573

B3702 and B3703
2.550781
2.550781
2.550781
2.550781
2.550781
2.550781
3.550781
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688
4.554688

[WicketMike]

thanks for the info, so it looks like you fixed it.

did you try leaving b3605 alone and only raising the b3702 and b3703 to 4.55 across the board?

[Black02SS]

Thanks for the info John. I have cleared out my PM's now so they should work.

[jfpilla]

Thanks for the info, John and clearing up the question about 3617. I'll try it next week.

Back to your original question. Why is A/F different on cold start with, versus without, the MAF? On cold start, with either, they are in open loop. Or has your solution fixed both states?

[WicketMike]

editdddddddddddddddddddddddddd

[bink]

Thanks for the info, John and clearing up the question about 3617. I'll try it next week.

Back to your original question. Why is A/F different on cold start with, versus without, the MAF? On cold start, with either, they are in open loop. Or has your solution fixed both states?

Joe - my bad on the offset table suggestion- I dont know what I was thinking!!


Through the MAF the PCM goes through the airmass calculations and crutches the predicted airflow- crutched injector pulsewidth determination.
Without the MAF (SD) it's more straight forward using the VE table, IAT, MAP, RPM etc.
Open Loop - no O2 sensor input.

gameover posted this AIRMASS Calculation info on LS1Tech ... it really helped me get a little better understanding of fueling via the MAF versus SD. At one point in time I had three copies of this Airmass post conviently scattered around the house so I could review it as the need arose. True - hardheaded analog man . AIRMASS Post -->http://www.ls1tech.com/forums/showthread.php?t=147645
I realize you know ALL of this......... God knows the number of times I've not had them straight in my head - I'm embarrassed to think about the hours I've wasted !!.

Cheers,
joel

[jnorris]

Well I really did not fix the problem; I just covered up the symptom.
Actual AFR verses commanded AFR differed by an average of 2 points during the 1st min of the cold start.
The next min the AFR was off by 1.2 points, the next by .8 points, and the next min by .5 points.
See attached picture. The bottom graph is the WB AFR (yellow), commanded AFR (blue), and ECT (green)




Why is this happening? Well I had the idea that maybe the purge solenoid was being commanded on up to a certain temp by default if there was MAF failure. I logged GM.EAVPDC but it was never commanded on. I knew it was a stretch but I did not know of any other way air could get into the engine.

With a MAF tune there is not a cold start lean condition. But on the next cold start I will check.


John

[jfpilla]

Joel, John,
I'm only referring to the short time after startup, in open loop, with the MAF. In this state it's lean but not as lean Mafless startup. It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe

[Black02SS]

Joel, John,
I'm only referring to the short time after startup, in open loop, with the MAF. In this state it's lean but not as lean Mafless startup. It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe

I believe jnorris stated to me before that he didn't notice the car runing lean with his MAF plugged in. I am going to re-install my wideband tonight and will be able to help you guys out as it is colder then snot here.

[bink]

Joel, John,
It appears that Joel is making me read and learn about this.
Joel,
I have not spent any time at all on this part of tuning. I run the MAF and only use SD to tune the VE's and really have not paid attention. My goal has been to get idle and cruising tuned using as few tables as possible.
It will be interesting to work on something new.
Thanks for the help.
Joe

Joe ...HeHehe...... I know you know this!

I often get it confused...that's why I elaborated a bit.

The AIRMASS reference is for any and all lurkers/newbies. I always try to think of the newbies. You guys helped me out (as a newbie) immensely - I try not to forget that.

Cheers,
joel