What table should I look into for clues?

[CRU SS N]

I have a 99 SS with a 402 LS2 with a pretty big cam. It was tuned by a reputable tuner. Now I'm trying to figure out why it's going lean when I go into third (automatic). The injector duty cycle can be seen going from around 65 percent down to about 50 percent and the o2s fall off, but no other sensors I'm logging appear to be changing values to corelate with this change. Therefore I figure it has to be the tuning somewhere in one of the tables that is calling for this leaning out. Any help is greatly appreciated, because I don't want to hurt anything! Thanks, Brian

[GMPX]

Is it using a MAF or running in S.D mode?

Cheers,
Ross

[CRU SS N]

It's using a MAF.

[Tordne]

Try logging the GM.DYNCYLAIR_DMA PID and see what that does.

This is out there, but have a look at the B4107 table which defines which Closed Loop Mode to go into at various air Grams/Second.

Then also have a look at the B4105 table which matches those Closed Loop Modes against the O2 switch point (in millivolts).

My thought is that perhaps in 3rd gear the air volume might put you into a different cell, and therefore the O2 Switch Point may be causing your lean condition.

It is a bit out there, but hey, worth a look right?

Cheers,

[Forcefedperformance]

We Are Having Tha Same Problem On A 03 Hummer...I Have The Data Log If Any One Is Interested ????
This Problem Kicks In At 60-62 Mph At The 2-3 Shift Every Time.

Hey Blacky Any Idea's??


Bill
FFP

[superls1]

Do either of you have the tune file? It would be nice to also log actual Pulsewidth and Commanded AFR

Forcefedperformance -
MAF? My assumption is yes. What injectors?

Update
Definitely need to see actual injector pulsewidth. In the data provided, the Calculated Injector Flow Rate stays constant (.71lbs/min) during most of 2nd gear, but airflow changes from 30lbs/min to over 40lbs/min. Thus, would need to see what the injector is actually doing. To maintain a 12.4AFR, the pulsewidth would have to go up. Also note that the timing significantly increased from 11* to 18* just prior to the lean spike. Very interested in seeing the tune. :)

[Forcefedperformance]

Here is the Log Files With The Added PIDS..Itook the truck for a drive today and the first pull it did not lean out Run #4......The second Pull it leaned out but not between 2-3 this time It did it between 1-2 Run #5. the tune is to big to post...can i post it some where else?

[caver]

Anyone looking at fuel pressure?

[Bruce Melton]

Anyone looking at fuel pressure?
Pump?

[superls1]

Here is the Log Files With The Added PIDS..Itook the truck for a drive today and the first pull it did not lean out Run #4......The second Pull it leaned out but not between 2-3 this time It did it between 1-2 Run #5. the tune is to big to post...can i post it some where else?

I will take a look. You can email the tune to superls1@yahoo.com

I too am curious about the fuel pump/pressure and perhaps some voltage irregularity.

[superls1]

Here is the Log Files With The Added PIDS..Itook the truck for a drive today and the first pull it did not lean out Run #4......The second Pull it leaned out but not between 2-3 this time It did it between 1-2 Run #5. the tune is to big to post...can i post it some where else?

What size injectors? Also, I assume you have modified the MAF curve?

[CRU SS N]

I actually went to the custom operating system number 5 now and I decided to try out SD for a while. I eventually plan on running it with a MAF in open loop. Thanks for the help anyway.
Brian

[GMPX]

Brain, if you are going to the trouble of tuning it in S.D or off the TPS then why would you refit the MAF?,
I must admit, the TPS mapping has never been tried with a MAF, the engine combo's that would require TPS mapping would cause some serious reversion issues with a MAF so people would not bother.
I have not run O2 sensors for a long time now (well, I use the load v's AFR map), and my engine still runs the AFR's I want all day everyday, no MAF, no O2 feedback (apart from the WBO2 of course). Once everything is dialed in then there is not much need to rely on O2's or a MAF to keep the tune in place.

Cheers,
Ross

[CRU SS N]

I have read where the MAF makes the car more consistant from day to day through weather changes. As long as I can get the SD tune on the money than I won't care about adding the MAF, but I'm battling an issue now. I get the car to where it is on the money in auto VE, but then as soon as I turn it off and restart it the next day itdoesn't want to idle or drive at all. It will be very lean until it gets up to operating temp. What I don't get is it used to idle perfect until I did the autoVE tuning.