Very bad idle in cold weather, where to look at?

[Vetal]

As weather got colder (below 40F) and very humid, I started to have terrible idle on my 383ci LS1. After cold start, it won't idle without throttle. Then when it is warmed up, it still very often wants to stall when I come to stop (auto tranny). After some 20 minutes of city driving everything is normal again, drives and idles fine. It didn't do this in summer or autumn. Where should I start looking at?

[WS6FirebirdTA00]

Post your tune and idle log.

[Mobius]

I have same problem... subscribing!

[Vetal]

Here is one very good log from today. As you can see, I had to hold throttle a bit (2%) all the time, and when I released it, the engine died immediately.
All the values jump around and I don't know which is at fault...

[turbo 6l]

i would start with fuel/general/ injection timing/normal ...adjust as u see fit ..also one other note to make i know the rpm was up and down all over the place but your ignition voltage is all over the place 12.45 to 13.8 ..this also play havoc with with the injectors ..fuel/ general/offset/..offset vs volts vs vac....hth happy tuning

[printmanjackson]

it has to be fuel because you say it was fine in warmer weather. SO, what fuel table does it use as it's warming up?

I would start there

[Vetal]

i would start with fuel/general/ injection timing/normal ...adjust as u see fit ..

do you really feel like you have given the good advice? "engine stalls so adjust fuel/timing/general", really?

also one other note to make i know the rpm was up and down all over the place but your ignition voltage is all over the place 12.45 to 13.8 ..this also play havoc with with the injectors ..fuel/ general/offset/..offset vs volts vs vac....hth happy tuning

that's quite understandable imho that voltage drops when revs drop down to almost 300...

[Vetal]

it has to be fuel because you say it was fine in warmer weather. SO, what fuel table does it use as it's warming up?

I would start there

has to be either fuel OR idle valve, but I cannot see anything obviously wrong...

[WS6FirebirdTA00]

First fix your TPS, it thinks it is at 2%.

What size cam? Next guess would be to bump up the idle speed and give it more adaptive spark for control. Right now PID idle control is not active since it thinks you are giving it throttle. Look at your IAC, it isn't moving.

[eficalibrator]

I will agree that this is probably a fuel delivery issue. HOWEVER, it has been my experience that lack of AFR control at hot/cold temps is often a symptom of a more fundamental problem. If you tuned the "normal" temperature VE and MAF tables around incorrect injector characterization data then you likely "baked in" some error to the airflow tables. Now that there's a significant change in air density, you're starting to see that the injector error that was baked in previously no longer follows the simple science of air density changes with temperature.

Unfortunately, this usually means you'll have to start over with GOOD injector data and retune. If you don't have accurate data, well......

[Vetal]

First fix your TPS, it thinks it is at 2%.

As I said... I had to depress pedal so it could idle... Thus 2%. When I released the pedal it died...

What size cam? Next guess would be to bump up the idle speed and give it more adaptive spark for control. Right now PID idle control is not active since it thinks you are giving it throttle. Look at your IAC, it isn't moving.

Thunder Racing cam 214/220 .600/.523 115LSA.
Yes, I have to give it a bit of throttle to idle. And this is the main problem

[Vetal]

I will agree that this is probably a fuel delivery issue. HOWEVER, it has been my experience that lack of AFR control at hot/cold temps is often a symptom of a more fundamental problem. If you tuned the "normal" temperature VE and MAF tables around incorrect injector characterization data then you likely "baked in" some error to the airflow tables. Now that there's a significant change in air density, you're starting to see that the injector error that was baked in previously no longer follows the simple science of air density changes with temperature.

Unfortunately, this usually means you'll have to start over with GOOD injector data and retune. If you don't have accurate data, well......

I think about this possibility too, I got excel file from FIC Injectors but there was some confusion with it so I'm not 100% sure

[WS6FirebirdTA00]

Sorry I missed that. Didn't think you could hold 2% that steady lol

Seems to me it wants a lot more air than it is getting. Just for the hell of it I would jack up the idle airflow and see if you can at least get it to idle on it's own. That could help tell a lot more.

[Vetal]

lol )
OK I'll try to increase Base Running Airflow -> Idle Airflow in cold area...

I see that my stall saver tables are zeroed - is that right???

[turbo 6l]

do you really feel like you have given the good advice? "engine stalls so adjust fuel/timing/general", really?

yes i do think iam telling you correct Labels -40 -18 3 25 46 68 90 111 133 154 176 198 219 241 262 284
EOIT (Ref periods after boundary) 2.551 2.551 2.551 2.551 2.551 2.551 3.551 4.551 4.551 5.551 5.551 5.551 5.551 5.551 5.551 5.551...if you notice here off your tune posted 2.55 when it is cold and 5.51 when it is warm..... then gm thought it be cool just turn it down when cold and turn it up when hot ...hmmm adding fuel when cold less when hot geeeeeee i wonder...if you do not like this idea then kill all of your afterstart enrichment when cold 100 degrees or less ..the numbers above are really important especially if you have cam . which by the way you have not mentioned ..i am just assuming if your going to stroke a motor you are not going to put a stock cam back in hth happy tuning

[turbo 6l]

eoit= end of injection timing fyi

[turbo 6l]

also follow where i am telling you! windows at top of screen with your tune open engine / fuel / general / injection timing / normal ....... really

[Vetal]

turbo_6l, my bad! I didn't realise you are pointing me to specific table, sorry!
That end of injection timing table looks stock to me...

[turbo 6l]

vetal if i come across as a butt ..i am sorry i just do not post a lot on here because i was just doing a lot reading and trial and error on my end .and i do think i have good understanding on these ecm .the new ones e38-e67 that is another story and still a work in progress any way hope you get it worked out and i hope that where i told you to go does the trick...it will help but i am not 100 percent confident it will fix all of it. (what will i am pretty sure) is this plus all of after start enrichment same screen as i told you above( previous post) just under stioch is afterstart enrichment (decay delay) from -40 to 133 turn it down to like 15 engine revs / turn all these down too like 133 degrees make all these from -40 to 133 put in what is in 133 you will also have do the same for pn/drive enrichment turn down the revs to like 15 instead of 64 across the board this will help all of extra fuel you are getting in cold start up hth and happy thankgiving to you and yours

[WS6FirebirdTA00]

I don't mess with that. I have tried and I see no real benefit to where it is considered a must on a majority of the typical setups.. Just my opinion.