Idles but dies when put into gear

[animuL]

I just put a brand new 408 in my 98 Vette. Its got a 240s duration cam and about .625" lift. For now its got a stock TB (electronic throttle), 78mm FAST intake, PRC 237cc heads, 10.3:1 compression, pump gas, stock exhaust minus cats. I started out with basically a stock tune, except I have 45lb injectors compared to the stock 28lb so I simply added 17 across the board to my injector flow rate table (is that the right thing to do?). The car fired right up and would idle in park so long as I used the real time controls to hold the idle at 1000. That was on a 65° day. So then I set the car down and put it in gear and it stumbles and dies. Mind you the car ran perfect before with the LS1 and I have changed nothing in the transmission and as far as I know its got a stock converter. In other words, I have every reason to believe that I am dealing with a tuning issue here, not reason to believe at this point that its a converter solenoid or something. If I hold the throttle at about 2500-2000 rpms and put it in gear it will stay running and I can drive it around so long as I keep some gas in it when I stop. I found a thread on here with a pretty detailed how-to guide for tuning for a cam (fwiw my Camaro has a similar sized cam in the stock cube LS1, I tuned it myself and did none of the stuff in this guide and it idles just fine). So anyway, following the how-to guide I got all of my timing tables (idle in P/N, idle in gear, high octane, low octane) smooth and consistant so that the timing doesn't make a big jump. I set my idle rpm to 900 all across the board, set the EQ ratio to 1.13 for about a 13:1 afr (I just have narrowband at this point). I added a few g/s to the idle airflow table. I left the MAF and VE tables as they were. I entered in the new cyl volume for a 408 and set it to 6.0L. After all that, the car is about the same if not worse but its been 40° now so that could play into it. I'm not an expert on IAC position but I did notice it was at 160 which I read is pretty much wide open. The electronic throttle stays at around 14% at idle. So basically where I am at now is that I can start the car and it will idle in park, then when I put it in gear it stumbles and dies unless I am giving it some gas. Even when its warmed up to temp it does this. Any ideas on where I should start looking? I'm planning on dyno tuning it but I am waiting for a bigger fuel pump to come in so I have time to work on it and perhaps save some time and money on the dyno if I can get that part of the tune closer.

[animuL]

Okay so after thinking about this some, I guess I dont even have an IAC since its electronic throttle. I guess that narrows it down a bit. I figure with a stock (tight) converter I get quite a lot of load on the engine when putting it in to park so in order to maintain RPM I need to make the engine more efficient in gear than when it is not in gear. So I went back and reduce idle timing for park and neutral. This goes against what I read in the ho-to but it made sense to me so I tried it and... it seemed to work, I can put it in gear now and it doesn't die. Its not perfect but it works kinda. Not good enough for the daily driver that this is but its a starting point! It does stumble around some but I figure thats probably in the fueling.

[animuL]

Yep, played around with the VE tables and it idles great.

[BlackZLS1]

If it helps, your cylinder volume for a 408 is not 6.0L, what the computer wants to know is the volume for each cylinder. So for a 408 would be something like .836. Thats what I have my 408 set at.

Sounds like you need to set your base RAF tables. Theres a write up here somewhere with some configs to try. Search for cam idle tuning and im sure you'll find it. In short, you want to run the histogram in that config, cold start park/neutral and let idle till warm, take the data from the log and paste into your tune. Save, reflash, repeat. Then let it cool down once again (good weekend of work) and do it all over again in gear. Probably should chock the wheels.

[JamesLinder]

My 408 is dialed in; try some of the settings in mine that deal with idle (base spark tables, PID, idle air park, running, start-up, etc)
My timing is a little lower because we can only buy 91 octane gasoline in NW AR, however my settings should get you up and running
and you can increase timing a little at a time beyond 1800 RPM to see what works best for your motor. Ignore my transmission
settings because I have a non-lockup converter with manual shift automatic.


Custom Built, Forged 408 CID LQ9 - TX Speed & Performance

WiseCo 4.030 -8cc Pistons, Lunati Rods, 24x Lunati Crank
199-AsCast, Precision Race Components Cathedral Cylinder heads 68cc; 10.7:1
Custom Order Comp Cams: 227/235 .614/.621 on 112LSA
PTM 102mm Throttle Body, Fast Toys 104mm Air Cleaner Lid
FAST 102mm Cathedral-Port Intake Manifold (146302)
TSP 100mm MAF, 2006+ Corvette Z06 GM MAF Sensor
Kooks Long-Tube headers with Y-pipe; CATs removed
GZ Motorsports LSX Series Sportsman Crankcase Vacuum Pump Kit
4-Speed Manual-Shift 4L65E Automatic Transmission
Meziere 680-WP319S Electric Water Pump
Racetronix Fuel Pump Kit
2000 Camaro OEM PCM

[blownbluez06]

Got this fixed yet?

[THE CHAD]

need the correct injector data for those squirters....cam that big will need a bigger conveter(loose) so you can set the correct idle without any pushing dramas...check spark tables etc...get a wideband dude that is the ONLY WAY TO TUNE...ps every engine combo is different as a example I run my spark tables idle in gear/park different from each other in areas and also my spark tables from those two aren't the same as my high octane/low spark tables and mine drives beautiful and doesn't stall when pull in gear and he goes like HELL and runs 10's and only idles at 640rpm when at operating temp all on a stock bottom end ls1...this is only my opinion on things so what works for me and others may not work for you mate so trial and error and use the controls...gd luck