LS2 idle issues cold

[ratnfested]

I have a 5.3 .100 over Gen 3 PCM
mild cam
dart heads
ls2 intake, plans to upgrade that later

My issue is when I goto drive it and put it in gear, it idles fine but if I let off the brake and the car beings to roll the idle go nuts and surges and stalls and I may be rolling at 1 or 2 MPH. I can restart it and it will do the same thing again when I let it roll. I have to gas it to avoid that situation.
However once the engine is warmed up I can turn off the car and restart it, at that point it usually will start running good and rolling will not affect it anymore.
also when it is cold if I am driving it and come to a stop the engine does not idle down gently, it just drops right down. but after a restart when warm it will follow the speed of the car with a higher idle till I fully stop.

I attached the tune. I need to drive it and get some log data but with the issue being idling and slow roll I am not sure what it will show.

[ratnfested]

Nobody wants to take a crack at this?

[EWY]

Sounds like it needs more base running airflow in the cold temperature section. Upload a data log of the issue so we can better assist you. What all have you done to the Tune?

[ratnfested]

I have lost track of what I have done. Because its been an ongoing issue for 4 years. And I tend to forget about it and not drive the car for some time. I record what I change as the filename of my tune so I can look back. I will get a drive log when the weather stays nicer and I can drive it. Thanks for replying.

I went back and looked over what I have done. I started with a stock 2500 6.0 tune cause I have a 4l80e. I modified the MAF cal based on a spec that came wit the MAF. But I found it to be way off and adjusted it last year using a wideband O2 sensor to get my AFR in a happy place. I used to have surge issues from it being too lean cruising. it was annoying with the TCC locked up. So I made tons of headway for idling warm right through WOT. If I recall correctly AFR is 13.x cruising and pops into the 12's at WOT. I did lose closed loop on a recommendation from a friend. That was the start of all these changes last year. But the thing that never went away no matter what I change is that the idle when cold or after an hour parked, will be fine as long as I do not let the car roll any slight bit. as soon as there is a speedo signal it starts surging and cannot maintain idle and will stall. But again, if I let it idle a couple minutes and shut off/restart it then the idle acts as it should. It will rev up if I touch the gas and come down nice and easily. and when driving I can tell the RPM stays just under the trans rpm and comes down gently as I stop. Might disconnect the speed signal and drive it. I can jack up the back wheels, idle the car in gear and if I let the rear tires roll, surge surge stall. Its totally screwed up.

[ratnfested]

I just realized I have a log file from last year where it stalls right when I start moving at 1mph. all starts about 20 seconds in.

Thanks

[kevin87turbot]

I just realized I have a log file from last year where it stalls right when I start moving at 1mph. all starts about 20 seconds in.

Thanks

The tune is jacked up pretty badly. I'll give you a list of the bigger issues.

1. The ignition timing is WAY too high for pump gas. I've tuned NHRA Stock Eliminator cars that run less timing on C16 race gas. If you're running 93 octane pump gas, you will need to reduce the WOT timing by 10 degrees.

2. The VE table is unusually high at upper rpm. I've seen this a few times, but usually it's compensating for a weak pump or other fuel delivery problems.

3. The throttle cracker activation and deactivation mph is the same. I'd recommend increasing those to 255/254 respectively for now.

4. The base running airflow table is nearly stock. You'll want to add at least 5 or 6 g/s to the entire table for now.

It would be a good idea to install a wide band O2 sensor and get the VE table dialed in.

[ratnfested]

Thanks I will go through your suggestions

I run a carbed big block in another car and I always ran 38 degrees timing wot, so that habit rolled into my attempt at an LS. Although knock sensors are pretty quiet on this setup.

I did add a bunch to the base running airflow last night, but its raining and testing will not happen till tomorrow.

VE I can believe, AFR gets fat at WOT. But not horrible. I can work on that too. I did alot to the VE last summer with a WB o2 but let the top end stay fat.

I assume you want me to disable throttle cracker, Those numbers were from a stock 2500 6.0. I didn't understand why it was that way.

Thanks again