Hi all,
Been reading this forum for a long time, but this is my first post. I have a 95 Tahoe with a (96-02) STOCK 350 Vortec motor. I am running my original 95 TBI computer 7427, and it has been modified to run in batch mode MPFI.

Tahoe runs great, but have a cold start problem I cannot seem to find a solution for in the BIN. I am using TunerProRT V5, and the $0d mask.

My problem is the motor will start right up, when cold, but then it stalls almost immediately. The very next start, 2-3 seconds later, it will start right back up, and run perfect, fast idle slowly decays away to normal idle as the motor warms up.

I have adjusted the "crank BPW vs. temp" parameter originally set at 123.49. I have read that the old TBI setting would normally be rich at cold start, and now that I am running the Vortec motor, I wouldn't need as much fuel for the cold start. I have lowered this number down to about 90, anything lower than that, and the motor needs to crank too long to start.

Recently, I have found raising this number from 123.49, to 150 has helped, somewhat. I am not sure if I should keep raising this number? It seems to me I am going in the wrong direction?

Are there any more parameters I can adjust on the $0d mask? I have read about “after start fuel”, but my 7427 computer doesn't have that table. Where else can I look? Any help would be greatly appreciated.

 

After start fueling table starts at $4C29:

RBob.

 

Hi RBob,
Thanks for this info, I'm happy to know there is AFTERSTART fueling adjustments in the $0d mask, but I am a novice tuner, and do not know how to use this information?

 

I have been meaning to check out you .BIN that you sent me. Just need to find my flash drive and load it to my tuning laptop. It helped me to copy over many of the 4.3 CPI settings as they were a better starting point than the TBI stuff.

 

Hi Fast, No worries! I know your a busy person, and I really do appreciate your offer to look at my .BIN to see what I was/am doing wrong.

The push in the right direction from RBob has helped a lot. I didn't understand the Hex address he quoted me, but with some more googling, I was able to match "L4C29" to "choke AFR vs. Temp" in the $0d mask.

This morning, I made the following changes:
I added 50% fuel to all the values in the "choke AFR vs. Temperature" table from 20C and colder.

I changed "Time Before Choke AFR Decay" from 2 seconds to 5 seconds.

I doubled the values of "Choke AFR Decay Time vs. Temperature" all values from 20C and colder.

Loaded up the new BIN, and started the motor at 58F, plenty cold enough for the cold start stalling problem I was having, to force a stall.

This time, the motor started right up, and didn't stumble, or dip the RPM at all, just right up to fast idle, and smooth. This is the first time this motor has started this cold, without stalling since I did the TBI to CPI/MPFI conversion last summer.

So over the next several mornings, I am going to back out the choke fuel until I find where it really needs to be. I think adding 50% may be a bit extreme.