As seen in the datamaster window below the spark advance at idle is very erratic, anywhere from 14-25 degrees of advance. This has been going on for as long as I can remember on many different bins. What would cause this?

 

Idle stabilizer SA. For your setup I would reduce the magnitude of SA corrections. Only need enough SA correction to prevent the idle from rolling.

RBob.

 

Rbob,
Are you reffering to L81FD ? (Terminology getting the best of me)
I only see that stepping between values there would only yeild about 5 deg SA with the idle as stable as his log indicates.
He is jumping 10.
Are a combination of SA correction attempting to work there?
Something like RPM error combined with crossing the 800 rpm boundary of the closed throttle table.

 

There are 4 tables at $1EB, $1F0, $1F5, and $1F9. Then some qualifiers and multipliers from $1E5 through $1EA.

If the RPM is too high some timing is pulled out. If the RPM goes too low then timing is added. Helps prevent the idle from rolling, or slowing increasing and decreasing in slow motion.

RBob.

 

Ahhh... I'll do some tracing to see how that all works together.
Nice new site BTW, good job

89' if you get a chance to make some changes on those please post up your results. I did have a slow rolling problem last year as well but was not dramatic. I'm surprised the RPM did not change that much during those transitions on the log. might have made it easier to spot that the RPM was triggering the spark changes.

 

I did make some changes to the tables, etc and it smoothed out the effects of this. Might just be my combo reaction but it has shown me some benifit.
The $1E6 threshold value was raised to 1000 rpm.
My Idle was crossing the original 800 RPM boundary continuously so I raised it to keep things consitent.
The table at $1F0, "Idle Spark Advance Vs. RPM Error"
reduced by 1/2 the values to 2.5 at 0, 50, & 100 levels.
The table at $1EB, "Idle Spark Advance Retard Vs. RPM Error"
reduced by 1/2 the values to 2.5 at 50 & 100 level.
The retard table had zero at the "0 RPM" error so I left that alone.

Reducing the amount makes the spark only travel +/- 3-4 degrees.
If the error was larger than where I changed then I figured a large 4.92 change would be benificial.
Results showed up nice on the log. Idle did not wander like before due to the overcorrection that was taking place.

 

TTT for good info

 

i though i would add to this.

i was also having a problem with my idle surging up & down. it would also intermittently die when i went to reverse. by intermittent i mean it would do it maybe once a month.
i couldn't find anything wrong anywhere other than my idle timing bouncing all over.
i changed both the idle spark advance & idle spark retard Vs RPM.
i set both advance & retard the same. at 0 RPM error i set timing change to 0,
for 50 RPM Error i set the timing change to 1.05, 100 RPM error to 2.11, 150 to 3.87, & left 200 RPM at 4.92.
doing this helped smooth out the surging idle alot. it still had some surging but it was something i could live with.
i still had the intermittent dying problem when going to reverse.

later on i started having intermittent hard starting & sometimes a no start unless i got a jump from a running car. when it wouldn't start without a jump it would surge again for a few minutes. i finally pinpointed the problem to a bad ignition switch when it wouldn't start one day.
i found it by looking at the data stream & noticed the battery voltage was showing just over 10 volts with the key in the run position. cranking the voltage would drop down to around 9 volts. the new ignition switch brought the voltage up to 12 volts in the run position & 11.6 cranking. it starts every time with no problem, doesn't die when going to reverse, & has a rock steady idle.

 

I saw the same problem with fluctuating idle when a moroso 4-way disconnect switch was on its way out. End result, you need a good alternator and wiring for a good idle for starters. One-wire alternators are not that great for EFI stuff. If the voltage bounces it plays with the injector BPWs too much and makes it hard for the CL code to handle. The injector battery offset can be tuned but it is tough to do with a bouncing voltage.

 

Worn dissy gear and or cam gear.

 

Sorry for the dumb question, but what is the title of the table $1E6 in the SUPER_8D XDF file?

I cannot seem to figure out where this is........ none of the table show 800 rpm as an idle parameter