I'm workin on an OLSD tune for my 4.8L 208/230 121lsa truck. I have been having some issues with start up airflow correction and airflow correction when going from park/N to gear. I made some aggressive changes to most related tables trying to get a result. I changed B3628 from 4 to 10 across the board and the truck would start up and come to an idle. It worked good for a couple of starts and then it went back to needing throttle input right after it starts before it can idle on its own. Any suggestions or tips? I'll get some logs tomorrow, if any PIDs would be helpful let me know.
Thanks

 

With a 121LSA and that duration, you shouldn't need much correction at all to get it to start and run. Changes to the tables you've made shouldn't be required. One thing that you definitely do need to do is adjust A0008. With the Commanded Fuel by RPM replacing the previous warmup AFR table, you're set to go into closed loop immediately and that's not good. Something like this would do you good.

LABELS Open Loop ECT Commanded Fuel Multiplier (Factor)
ECT °F {link: SAE.ECT} Value
-40 1.200000
-22 1.200000
-4 1.200000
14 1.200000
32 1.200000
50 1.200000
68 1.180000
86 1.140000
104 1.070000
122 1.020000
140 1.000000
158 1.000000
176 1.000000
194 1.000000
212 1.000000
230 1.000000
248 1.000000
266 1.000000
284 1.000000

(that's in EQ)

I'd also change the Blend IAT with ECT back to Yes. With your radix truck, having the IAT sensor located in the manifold, charge temperature blending isn't as much of an issue as it is with this new truck with the stock manifold.


With any increase in desired idle speed, will come a need to increase the desired airflow table (otherwise the PCM will have to learn much more to idle properly). With the larger cam and higher rpm, I would suggest increasign that table by 1.5g to start off. This change alone may fix your idle problem.

How does your timing at idle look. Jump 2-3 degrees or does it swing violently?

 

Thank you Justin. I made the changes you mentioned and put the other tables I messed with yesterday back to stock. The truck started up and came to an idle OK with 127*F coolant temps. When the temps came up a little bit, ~170*F the truck did not want to start and come to an idle.

I don't have any O2's hooked up on the truck, is it still possible to go into a type of closed loop?

I got some logs of startup, you can probably tell more of whats going on from these.

 

Here are the rest of the logs and a recent .tun.

 

Ah, yes. Your B3647 table has 1.0 for many values... when at 1.0, it will use short term trims. Set it to 1.01 or .99 for all values of 1.0.

Does it start if you give it throttle?

 

Next, I need to see you log the following items from a cold start idle til it gets warm (if you can).

GM.IAC_LTPN_DMA
GM.IAC_STPN_DMA
CALC.RAFPN

This will tell us how much more air you need.
Justin

 

Yup it will start and come to an idle if I give it some throttle after cranking. I'll set B3647 to .99 and try again tomorrow. How do the short term trims work?

The next time I will be able to log will be tomorrow when I get home from work. The truck will be warm then, how cold should it be before I log the PIDs you listed?

 

Log those at any time and just let it sit and idle. Those will tell how much air needs to be added or removed from the Desired Airflow table.

Justin

 

justin helps out everyone! great job...

 

I don't even have EFI live and I appreciate your help justin!!

HENRY!!! Stop blowing your **** up!