MicroSquirt.com read only forum (Jan.15,2018)

While the car is ideling. the a/f starts slowly goes lean until the car almost dies, then comes right back, and starts going lean again

Ms-II
v3
MT

fast2300tbird,

Pleae post a datalog, this will make it much easier to see what is going on and suggest fixes. To make a datalog, see this: http://www.megamanual.com/megatune.htm#fl

Lance.

As the idleing rpm drops the MAP will increase.
I suspect you need to increase the VE on your lowest rpm band in the area above the normal idle MAP.

see for example
http://www.msefi.com/download.php?id=4638

post a datalog, that should should show this.

fast2300tbird wrote:While the car is ideling. the a/f starts slowly goes lean until the car almost dies, then comes right back, and starts going lean again

Sounds to me like your O2 correction is coming on while the car is at idle -- turn off O2 correction and see if that fixes the problem. When O2 correction reaches the limit you set in the "enrichments" screen, it will "reset" itself back to zero and start over again -- this sounds to me like what's happening.

the afr seems to move all over at an idle..

check it out

Yes your AFR is definitely jumping around when it's idling... And according to that datalog, there is no O2 correction going on... That's weird... I'm at a loss... But someone else, I'm sure, will be able to look at this datalog and give you some suggestions...

well, thanks for looking at this for me.

could this be an ignition problem??

It appears that the lean spots correspond to a rise in map pressure, and a decrease in rpm, try richening those up. Also, you will find it is much easier to achieve a stable idle if you take some timing out, and make sure the timing doesn't really change as map and rpm wanders around idle. With the lower idle timing, the engine will require a little more air to idle, and also be much more reluctant to change speeds. I run 16 degrees around idle. Also with the ford 2.3, the factory computer idles at 900, so I wouldn't spend too much time getting it to idle lower than that. The main change I see is richen up the ve tables above 60 kpa in the region it idles. I would make a fairly large change (at least 20%) and see if it seems happier.
Something that is fairly helpful to keep from killing it is to put some "stall saver" timing in it. By this I mean add timing slightly below your desired idle speed. As an example, my desired idle speed is 900 rpm. I have timing points at 800, 900, and 1100 rpm. I have both 900 and 1100 set at 16 degress. I have 800 set at 21. If speed drops below 900 rpm, the extra timing will save it.
One final question, which ignition system are you running? If you are running tfi, set the predictor to last interval. I had massive idle issues when running tfi and the default ms2 settings.