Initial fuel prime question

[Rich Z]

Yes, the PCM see the the CPP (clutch pedal position) switch, it uses this to choose between the P/N tables or the IG (in-gear) tables.

Is that switch, or in any other way the status of "in-gear", monitored via a PID?

[joecar]

The is a pid, either STATExx or TSTATExx.

[Rich Z]

OK, I think I am making headway here...

The cold start tuning has been coming along pretty well, so I made up a video showing the progression along the way. I still want the initial startup to be stronger than it is, however. But at least I got the startup to be QUICKER after turning the key for the starter.

https://www.youtube.com/watch?v=edI3F-yjnGA


I was feeling pretty good about the progress I made when I started up the car on Saturday morning to go along on a cruise up to Thomasville, GA. In the past when I would start the car up, I would just leave my foot off of the gas pedal completely the entire time till I let the car warm up a bit, but this time I goosed it a little bit and the engine just fell right on it's face when the rpms came back down to what should have been idle speed. I cancelled the trip, not knowing what the heck was going on. Later on in the day when the car had cooled down sufficiently, I loaded in one of the old tunes from my tuner and tried the same gas pedal blipping thing, and it did the same thing. Apparently it isn't anything I inadvertently introduced with my own fumbling tuning efforts. It's just something that hasn't been addressed yet in this tuning effort.

<continued below as apparently only one video is allowed per post here>

[Rich Z]

So yesterday I set up the laptop for logging and also had video running when I did another cold start to check out this problem. I then took video off of the laptop and merged that video with the audio of the car actually running so I could watch the log data while listening to what the engine is actually doing.

https://www.youtube.com/watch?v=eogTdJ-l9aQ


Obviously I had to cut and paste sections of the video of the log file to fit the audio, as it appears that one or both are not actually in "real" time compared to the other. But it is close enough, I think.

So apparently I still have more work to do in this department concerning the cold start process. The engine is running in open loop at this time, so I need to figure out what tables would be active when the engine is coming down from an abrupt blip to the gas pedal and try to compensate for this transition that allows the rpms to drop down into a stall. It is only an abrupt transition that causes this problem, as a slow pressure and release seems to work OK.

Ah well, more digging...

[Rich Z]

Well, the most obvious event I can see when the engine stalls after the throttle blips is that the throttle blade opening goes from the normal 17.3 percent down to 14.1 percent, so apparently the engine is starving for air flow, which chokes the engine at the lower ECT levels. Once the temps reach a higher level, then that throttle blade choke doesn't affect the engine as drastically.

Anyone got any ideas on what table(s) I need to address to get that throttle blade to come back down and STAY at 17.3 percent after the jabs at the gas pedal?

[ScarabEpic22]

Have you adjusted your idle airflow tables at all? I know for the F body (cable TB) you need to do RAFIG and RAFIP/N, but I dont know about the Vettes. I had to add a bunch of air to my TBSS when I went to my longtubes and 4" intake, but the tables wont be the same (LS1 vs E67).

[Wheelz]

I had that exact problem 2 months ago when I got my 05 5.3 silverado (i have no idea why.. its bone stock). I bumped B2706 max etc idle contribution from 4.69 to 6. Mine would also stumble slowing to a stop occasionally so I bumped B4309 throttle cracker in gear 1000 rpms at 0 mph from 0 to .05. I also idle at 625 rpms, but that didnt seem to have any effect on the stumble after rev

You might also play with B4307 desired airflow to fine tune added airflow at each engine temp, which should open the blade up a little more

Edit: not sure if my table numbers will match (ls1b). I assumed the basic ones were the same

[Rich Z]

Thanks for the tips. This cold start tuning is a problem because I really only get one shot per day to try out any changes. So I'm changing several tables and will see if they help. Not the optimum way to do this, but with the temps warming up quickly during the day, I only have the morning to start the car when it is relatively cool.

[hog]

Excellent video's Rich. I have never seen video datalogging overlayed with engine audio, very nice thanks for sharing it.
I notice that right after the throttle stab the timing advance drops off down all the way to 0º and follows the rpm down as the engine stalls.
Once you are in Closed loop when the ECT reaches 115ºF your issues clears up. Even as the rpms come down after a throttle jab, the timing advance will NOT come down under 16º while engine revs never drop under 700rpm.

I just noticed that there is 2 tables for:
Base Spark Advance vs. Load vs. RPM(Closed Throttle, In Drive)
Base Spark Advance vs. Load vs. RPM(Closed Throttle, in Park/Neutral)

Does it make a difference if you push in the clutch pedal while in closed loop?

Your cranking times have come down nicely in your post #13.

peace
Hog

[Rich Z]

Thanks. Just seems to me that being able to actually HEAR what the engine is doing while viewing the log is beneficial. Sure wish EFILive could do something like this natively.....

Anyway, I'm just running out of ideas on this stalling problem. I made a lot of changes in the startup and idle sections and nothing made any difference at all on the engine falling on it's face when ECTs are cold and I tickle the gas pedal. I'm thinking the problem is with the throttle blade closing too far after I blip the accelerator and the RPMs come down. As for timing, well, maybe it's a chicken and the egg thing, but I'm thinking the timing is trying to recover from the engine going into a stall by pulling back on the timing. What exactly does the "stall saver" do that is mentioned in some of the tables? I've tried to figure out how to get that to kick in, but so far nothing I have done has had any effect. I looked at all of the enabling settings and tried to make sure they weren't inhibiting stall saver from kicking in, but either they don't do what I want them to do, or I'm still missing something.

So, reducing it down to as small a step as possible, HOW do I keep the throttle blade from closing up to 14.1 percent? How can I tell it to stay opened up at 17.3 percent to give the engine more airflow?

There are an awful lot of trees in this forest, so I'm sure it's just a matter of me not barking up the right one.

Oh, I forgot to try pushing in the clutch pedal during the stall area. I have the tranny in neutral, of course, so does the clutch pedal signal the PCM in some manner to command something different with the engine management routines?

I've attached the actual log file if anyone wants to see it natively.

Thanks....