Idle - Dies at Stop, OK when rolling!

[Kelp]

C6 Z06. HPTuners:

After 10-5 secs idle suddenly dies down then comes back up. Sometimes it dies completely. But if the car is ROLLING 2 mph it idles PERFECTLY. The closest table I find that differentiates idle from a stop and a rolling is OL & CL > LTFT Idle Cell > Enable VSS and Disable VSS which I set to 0 mph. I have been working on this for a month. Any tuners have any suggestions on tables to alter?

[DSteck]

Please list your modifications and post your tune file.

[Kelp]

Not a tuning problem. It is a switch problem.

All parameters PERFECT at "1" mph, and then switches completely at "0" mph, foot off the pedal all the time, going way lean, and dying every 10-15 sec.

Question is, what table switches this. I am looking all over for this switch - it may be in the BCM (and not accessable???)

[jimmyblue]

What you have, is an idle airflow setup that is either
unstable, or has bad "initial guess" airflow numbers
(base running airflow) that aren't high enough to
feed the motor. The throttle cracker (rolling > 1MPH)
adds more, enough to keep it alive.

When the idle is proper record the logged airflow
g/sec and make sure the base value (for ECT you
are at) is the same or greater. If you go a little
higher then the PCM has to work to bring it down,
not hurry its slow ass up to catch a fall.

The "switch" isn't the problem, it's the condition
(closed loop RPM control and not enough base
airflow) you are "switching" to. Problem can also
be worsened by a mixture error at low RPM, esp.
the 400RPM VE column which is hard to tune (no
data to speak of, in normal driving). When in
doubt, lean that one out.

[Kelp]

OK, I went and did those ideas. I raised up the lower part of my Final Idle AirFlow and the dying stopped. Problem is now I can't lower idle below 1500 rpm. I mean it dies if I lower the FIAF (Also tried Target Idle at 800 and 1100, and decr the timing) Also I adj the MAF g/cyl to match the g/cyl I was logging so the LTFT, etc was ok.

My LS7 does not have a VE table unfortunately I think, and not a throttle cracker for sure

I would like to lower the idle of course. Somehow make the car think it's rolling all the time, just don't know how to do it. I set all the VSS things to "0" mph, but no change.

I'm going to twist the TPS tomorrow and see if I can cheat it a bit. Maybe it is off anyway making the throttle plate open too wide at idle

[edd1025]

Post your tune so we can look at your base running airflow table. If you have erratic values in this table it's hard to pin down which row is creating the problem. The trick I've learned is to copy and paste the row with the highest values to every other row so that every row is exactly the same. Then see if that fixes your stalling problem. If it fixes it but the car can't bring the idle down start lowering the table by like 2% at a time until you get it where you want it and the car doesn't stall. At this point we are just trying to get the car to quit stalling and we will deal with higher idle or erratic rpm when the first problem is solved.

Ed

[Kelp]

Got it. MAF, etc did need some adjustments, I returned the FIAF to the previous adjusted tune. The key was in the min ETC settings, kind of like what the cracker does. Very perfect and wonderful result.