Saar

an intermittent oscillating idle brought this up, so i started researching on tuning PID controls, eventually came across this page:

http://www.online-courses.vissim.us/...controlmap.htm

interesting little tips that come up when you mouse over, a very current log shows this:



now, i used to have a random roll in the idle, maybe a 100 RPM in each direction, almost always happened given enough time, so i started playing with idle spark, ended up increasing it quite a bit in the idle SA modifiers (my modified A1 mask, BTW).

now, in very random occasions, when traveling between 0 and 10MPH with no throttle or brakes applied, the car will just start surging and generally won't quit until i either give it throttle or come to a complete stop. when at full stop, the roll goes away within a second and i have a pretty smooth and consistent ~700RPM(when hot anyways) idle.

so, i figure the IAC PIDs need some adjustment for whatever reason, since the IAC itself is nice and clean and otherwise responds nicely.

graph above shows IAC counts in hot pink(don't ask), desired idle speed in blue, and RPM in green. the oscillation seems to be more or less centered around desired speed, maybe shifted a little towards the low side, but not by much. it has gotten to the point of swinging so badly to stall, but it's even more rare.



based on those incredibly helpful tool tips, i'm thinking gain(integral portion, i think?) needs to be reduced?

i figure if i can nail this down after just a few hours of reading, it should be pretty simple for anyone to look at those graphs, find one that matches their situation and deal with it properly and easily. after that, apply the same principes to O2 sensors or anything else.

RBob

iTrader: (1)

Having gotten used to $88 code, I saw that the $A1 code is very much alike to it. There are some strange things is this code. I'm sure you know that an idle learn is required every time after the ECM loses battery power (just for the new readers...).

If you think that it is the IAC, then lower the gains by an equal amount. Try 10% at first. Then higher or lower.

RBob.

Saar

55->6D->88->A1, as far as i have searched back, they're all more or less slight evolutions of each other.i haven't done an idle learn in a very long time, but even when i did do them, the problem was still there, so i'd like to think that's not the issue... i got around needing to do the learns by watching what the IAC minimum eventually settled at after a learn and had a good smooth idle, then change the "initial IAC Minimum value after NVRAM fail" to that value, so whenever power is disconnected, the only noticable things that seem to get reset are fuel trims and residual knock retard that hasn't been filtered out yet.i've been chatting with someone i know who makes a living off of tweaking PID systems, i believe i picked up a good, consistent method off of him that i'll be able to apply if these intial changes don't give me the results i want.assuming i need to more or less start fresh(and disable the spark advance/retard idle stabilizer for my testing), i'll be posting a log of my notes and the general method/guideline i would be following.

Saar

the changes i made to the I tables caused some weird osciallating at almost every coastdown, so i threw the stock tables back in and i'll be starting fresh in a few days.