ChucksZ06

iTrader: (9)

I am using a wideband to get the a/f right and have increased the base spark in the idle rpms of the spark tables. I think my unstable idle problems are being caused by IAC not keeping up or being over active. What tables affect this problem. Remember I have ls1 edit. I have EFI live coming for the future tunes but this car already has edit. Any suggestions would be appreciated.

mr2guru

iTrader: (16)

I was/am having the same issue with my 408. It is really weird. It is a very STEADY idle but very unstable at times.

Played w/ follower tables, IAC tables, RAF tables, idle airflow, idle spark/control, stall saver, everything. It's pretty good now but if it gets upset, like fans kick on same time as when I'm turning and pushing in the clutch it may lose idle and dip. Once it starts dipping it may go into a fluctuation that it can't recover from. Jumping from 400rpm to 1100 and never recover to a steady idle, sometimes dying.

I can sit and manually turn on the fans, a/c etc... and it's getting the desired airflow and it doesn't dip or barely move from idle. But sometimes it just goes haywire. Like I said very steady, but very unstable. My RAF is correct. The STIT are in line... everything "looks" good when scanning.

I agree it has to do with the IAC not keeping up, being lazy, whatever. Once it goes into this jumping idle I can manually command higher IAC counts and it will recover. But it doesn't do it on it's own. I'm pulling my hair on that. Sometimes yelling at the IAC to act on its own.

Sorry, Im not of much help, but at least you're not alone

moehorsepower

iTrader: (3)

You unstable idle can be a result of a combination of incorrect IFR and or exceeding the parameters of the IAC, I tuned a car with the large TB and a FAST intake, When the LTFT were set to a slight negative, the idle would do as said, fluctuate, I also tried every other setting, Throttle Cracker, Decay ect. When I would set the IFR to the proper calculated setting, it would idle perfect but the LTFT were +25, This did not make any sence because the WOT A/F was at 12:9. This may be only one instance, but maybe go back to the basic and start over....

DrkPhx

iTrader: (15)

I have an LS2 402 and have the same exact problem. Though with my friend's help and some of my own tweaking I have gotten it much better, but it still needs work. If the fans are constantly cycling you may want to raise the settings. There is one table called Fan IAC correction which allows you to add airflow to compensate for the additional loads of the fans. In EFIlive there is a table for each fan. I noticed this really helped alot. Another table is Idle Flare control that may help also. Leaning out the main VE table from 400-1200 rpms and 15-35 kpa MAP by 2% helped a little also. My goal is to be able to reach into the car, crank the key, have it cold start right up with no surging and idle right away.

mr2guru

iTrader: (16)

Fueling everywhere is within +/- 0.5% (that took some time) I've tweaked the fan airflow tables and when the fans are manually engaged the desired idle airflow trims are in line. I'll look for an idle flare control, don't remember that one.

Cold start, hot start, all that is perfect. I get one surge then it settles into idle. Not bad for a 24x 110lsa cam. Once warm if I cause it to lose idle, say pull the clutch slowly in gear while on the brake, it'll start surging bad and the IAC does nothing to help recover and it'll just continue to surge until I either give it gas and slowly back it off or manually up the IAC counts.

I've pretty much learned how to drive around the issue. But it still bothers me.

DrkPhx

iTrader: (15)

Sounds like you have it under control and can give me some tips (hint, hint). There are a couple of tables for A4 cars under Mixture called Park to Drive Enrichment Delay, Rate and Factor, are there similar ones for M6 cars?

P Mack

iTrader: (6)

I would try increasing the idle adaptive spark and decrease the idle proportional airflow correction and see if that helps.

soundengineer

iTrader: (16)

the first key to tuning idle is to make sure you have the proper airflow...
check your hot IAC counts..if they are above 60 then you need to drill a hole in the TB till they are around 60...hot idle....

secondly you need a cold start and log LTIT and STIT's and get your idle airflow to fall in line...
when you see all temperature ranges having close to 0 on LTIT and STIT with fans off...then its close....usually after you change values you need to let it idle back to warm again to relearn...then check values and readjust accordingly until they are close to 0...a hair above 0 is better than a hair below on this...
next is to look at underspeed and overspeed spark...
sometims its too agressive...some times its not agressive enough...in general most people need to reduce the #'s for overspeed and increase the numbers for underspeed...
and then go to adaptive idle...Proportional.Intergal.Derivitave.
start with P and I...very rarely will you have to mess with D
not all os's have all of these parameters..some are very basic..some are very complex

you can make a suedo delta error by loggig RPM and desired RPM...and making an RPM error value out of them...telling to which values need to be changed or modified...dont go too far at once..small changes are definately your friend...
P is wide...I is medium and D is small variations...
start with P...get it to where all falls into I..then mess with I...and if you get it down to nitpick D...feel free...but usually thats only when errors are within 15prm either way

soundengineer

iTrader: (16)

make sure IFR is set correctly.....
and idle and WOT fueling has nothing to do with each other...
its all about what the VE table and MAF table show...