The build, 406 SBC, aluminum Vortec heads, 10.8 compression, chevy perfomance intake bored for 454 TBI, EBL flash.

I've got about 1000 miles on this build. The tune seems real good with lots of power and around 19-20 MPG.

The problem seems mostly with a hot engine, though I don't do much but hit the hiway when it's cold. Worse with the A/C on & electric fan on. Anyway at a stop if I have to idle long when I start to engage the clutch right at the transistion to forward movement the engine dies, usually so fast I have no time to react to keep it from stalling, starts right up and I can go.

Everything in this build is new so I'm scratching my head and looking for suggestions???

I wonder if it needs "pump shot" right off idle. I would try this :

1. add more AE TPS at 0-10% TPS and more AE MAP 0-50 MAP check if that helps. I would add 10% more. Be aware it adds only in increments of 61 usec

2. also reduce the TPS and MAP filter after trying #1 and see if it gets better

Be aware there is a "stall saver" value as well. May want to look at it. May want to move the RPM value for it up a bit so it can catch it sooner.

May want to ask moderator to move this to DIYProm.

what injectors are you running for that build and at how many psi?

Thanks Ronny,
That was what I was thinking but didn't know enough how to get there. TBI is new to me and I was wondering how to a bigger "accelerator pump shot" using carb terms so I will try your suggestion and get it loaded up tonight and see how it runs tomorrow.

UnderCover, I'm running 80# injectors at 13 PSI right now, I'm waiting for my new fuel pump to come in then I'll be upping the pressure.

Thanks all,
Lance

It either has too much or too little MAP AE. If you are datalogging, note if the o2 voltage is rising or falling when it stalls. Rising would indicate its too much AE, if its falling toward zero, that would be an absence of fuel.

Thanks, I will datalog it on the way to work tomorrow. I added AE TPS and AE MAP and bumped up the stall saver as suggested by Ronny and took for a spin down the road. It was a short trip but I did several stop and goes and it is much improved already. So with your help I'll get this figured out yet

Fast355, I'll look at some of my older logs and see but I'm pretty sure everything falls, when I first started troubleshooting this problem I was thinking it was electrical, did find I had a bad (new)TPS which helped with some of my off the line stumble but the stall out continued. I think I'm on track now but will let you know what I find tomorrow.

Lance

If its stalling out when you load the engine, it needs MAP AE, if its hesitating as you advance the throttle it needs TPS AE.

is that enough fuel to feed it? your still tuning it id assume so the fuel pressure isnt really where you want it yet.

I figured mine i need 454 injectors at 20 PSI to feed my engine to close to 6k rpms. and mine is a 355 with edelbrock performer heads, small cam.

No it's not, fuel pump on order. The important thing for me right now was to get some miles on it so that I'd feel good that it's broken in, so mostly just the usual drive back and forth to work. Flipped a thousand miles today so I'm ready to get serious about the tuning, just waiting for the pump.

Today's drive was much better and I retuned at lunch and added a little more MAP AE for the drive home and I think I'm almost there. Going to look over my data logs and see what I can see there and then probably massage things a bit for tomorrows drive in. Still learning...

Thanks guys!
Lance

Yes you will need a whole lot more fuel and a VAFPR and a WB for WOT A/F verification.

OK you just went way over my head, VAFPR??? what's that?

And while we're over my head let me ask, I've added an IAT sensor and was wondering what value I need to enter in the 'Blend Factor for CTS and IAT" table?

I used stock LO3 values. I believe you only change them to the same amount in each cell of table if you chose not to use IAT.

Variable Air Fuel Pressure Regulator. See Aeromotive 13301 for info. It is a TBI specific Reg. come with one spring 20 lbs and < and another 20 lbs and >. Some say it improves response in all areas of fueling.

sorry to thread jack but I have a question about that regulator. I figure I need 20# of pressure to feed mine to 6k RPMS. Not that i am going to turn 6k but ya know.

It says it comes with 2 springs one from 3-20 and one from 20-65. So if I need 20 at full throttle for proper fueling, I would run the smaller spring?

I guess my question is if I ran the bigger spring and had the fuel pressure set to 20. Would the vacuum refernce still lower the pressure to say 13 psi at idle or whatever? or would I have to use the lower rated spring?

Hope that makes sense.

The 406 sounds mighty close to what I have in my Blazer. What cam are you running?

The larger spring at 26lbs FP(for me) drops the FP to about 14. I would run the larger spring and check DC% WOT keep in 85 or under. I seem to get more DC in lower gear.

I gotcha. normally a 12 psi drop with these types of setup?

Sorry for the long delay, think I finally have it fixed. Wife noticed that when this stalling happened the spedo was jumping all over the place, I was too busy driving to notice. Once she mentioned it I started watching and logging, sure enough the MPH was jumping to stuff like 250 MPH+ and shutting down the engine, dang computers!

So I found that if I just rolled a little bit the speedo would go nuts and figured it was a bad VSS, changed it out $45 and nope that wasn't it... OK gotta be the PCM, order a PCM $135 (new rebuilt, wasn't going to mess with another junkyard pick) and hey no fix! *#@$%$#

So now I'm in about $200 and got nothing to show for it... Decided to look for the stuff I should have looked at first, found that I had routed the spark plug wires around and next to the VSS line... rerouted the VSS line and the plug wires and hey no more jumping!!!! Apparently was getting inductive pick up off of a plug wire at low signal levels (at a stop and just rolling) that did crazy stuff to the VSS input to the PCM. So add this one to your book, now I have to go back and reset the values I changed trying to correct this fault.

Thanks to everyone for your suggestions, now I can move on to the fuel pump and VAFPR.

Pumpkin, I'm running a comp cams H265 I think, been a while now since I put it in. Lots of torque, I like it

I was hoping it was a bit bigger so you could help me tune. I have
The comp cams 280XFI cam. I have it idling and revving fine enough to
finish putting the truck back together so I can start driving and tuning.

I'd be happy to send you a copy of my BIN file if you would want to use it as a starting point. Let me know.

Thanks for the offer, but I found one that works pretty close. It was a bin that came with the Dynamic EFI computer. Now its just a matter of getting my *** in gear and working on it. Its hard to get motivated when its cold outside and I work in a carport. On the upside I am getting paid to figure this all out as I am working out a tune for my boss on his 32 chev that I put dual TBI on top of a 6-71 blower on his small block.

I tuned a 406 with Dual TBIs on a tunnel ram in a 34 Chevy.

Cool. Did you experience any lag or backfiring when flooring it from a standstill?