Took a long cruise the other day and noticed that my rpms will go up and down from 1600- 1200 when decelerating from speeds above 70 mph in 4th gear locked, if im decelerating from 60 mph its noticeable. So I took a log today and noticed the spark advanced is jumping with the rpm change any ideas what could be causing this? Im using 8D with a slightly modified AUJP bin

 

here is another log

 

Took a look at the data...

I think the only thing in $8D AUJP that has spark related to vehicle speed is Highway Mode spark.

In your data, it seems like every time your spark timing starts "acting up" is when the ECM is in Highway Mode.

I'd check your settings for the Highway Mode spark.

 

Yes I was recently playing with the Highway mode enabling it, just looked at the bin and I have no spark advance with highway mode the enable temp is 304, I do have perform Highway mode checked off on the flag though gonna uncheck that and try again. Before the long trip the car did die while driving pulled over and noticed the ignition coil plug got disconnected. What I'm seeing in the log is that it turns off the advance completely 10.2 is what I have the base set at in the tune and it fluctuates from 10-30s while the rpm's jump

 

Yeah...It's almost like the EST connector is being intermittently disconnected, but I'm not seeing any code 42's being set.

Something going on with your ignition control module?

 

I'm going to test drive now went over the wiring to the coil will pull the G1 adapter and try straight aujp prom as well to see if its anything I did accidentally in the tune, I do have other ICM's that's in order for another day

 

Ok seems to be something in the tune with the factory PROM SA fluctuates from 22-27 on decel at the same mph soon as I stick the G1 with custom tune it drops to 10.2 which is the base. Even with the stock PROM though I do noticed the RPM bounce up and down as it goes from 27 to 22 from 70-60mph below 60mph SA stays steady on both chips

 

Seem to be getting somewhere I have been using v7 SAUJP and just tried it without doing to many changes to the original supplied SAUJP bin, noticed that they prioritize lock up decel at 70mph they have the convertor locked up and SA at base timing the whole time no fluctuating up and down when "tcc-bypass coastin unlock if not in dfco" and "unlock tcc in dfco" arent touched. I need to go back and read the notes from prior versions to see when they changed this and how to get the SA similar to stock where it doesn't take out all the advance when in 4th unlocked as my SA is good when deceling in 3rd or in 4th locked I dont believe I have a mechanical spark issue

 

This is happening during DFCO according to your logs also check your SA closed throttle vs RPM, SAUJP changes these settings

 

Just took a look at your second log.

First off, you have to understand how ECM calculates SA in S_AUJP 7730. Maybe a few searches in forums will yield some good info. Be prepared to read and pull your hair!

In closed loop with positive TPS, SA will vary with RPM, MAP and CT. That is essentially the main calculation. After that, there will be adjustments due to PE and HWY. There is also Know Retard (SA) and Low Octane Retard Routine. In closed TPS, there is a specific table for SA. It only involves RPM and the adjustments. However, idle RPM is being adjusted by varying SA (more tables!). The adjustment can be +/- 5*. In Open Loop, there are more tables involved to adjust SA. To add to the madness, there is a cold SA function that establishes SA differently using SA main table when CT is under a certain threshold. So it's a complex system.

To be specific to your original concern. On deceleration, there are 2 phases. Deceleration Enleanement (DE) and Deceleration Fuel Cut Off (DFCO). In DE TPS is not necessary 0% but in DFCO, TPS will be 0%. So, SA can be established from 2 different tables. What I have observed from datalogging is in DE, SA is being adjusted by up to -5* from original calculation. In DFCO, SA is reverted to base timing. In DFCO the injectors are shut off (no fuel). You can monitor DE and DFCO by datalogging. There are DE Status and DFCO Status PID.

DFCO sensitivity can be adjusted. You'll have to look-up the tables and constants. It's a lot to absorb!!!

What I see from your log is that you were cruising at 67mph, 2000rpm, TPS at 5% and you let go of gas pedal. DE was activated, SA pulled back a bit, RPM and speed started decreasing. DFCO was commanded, INJ shut off, SA went to 10.2* (initial), RPM and speed decreased (slowing down!). By 1100 rpm, DFCO was exited, SA bounced back so as RPM (vicious circle). ALL NORMAL.



I would:
Reduce "Continue DFCO if RPM >" to 950RPM
Reduce "If NOT in DFCO, Allow if RPM >" 1000RPM
"Continue DFCO if MAP <" 32KPA

You can experiment with that. The idea is to enable DFCO to stay on longer and avoid fuelling coming back on too early. Do not disable DFCO.

Good luck!

 

Thanks SbFormula!
I just noticed in TP "If NOT in DFCO, Allow if RPM" is 1400 for SAUJP and when using the compare feature comparing it to a stock AUJP bin it still list the stock bin at 1400 but when reading the notes or opening that stock aujp bin with a stock XDF it is indeed set lower at 1100

 

Just to clear the air

"seems to be something in the tune with the factory PROM SA fluctuates from 22-27 on decel at the same mph soon as I stick the G1 with custom tune it drops to 10.2 which is the base. Even with the stock PROM though I do noticed the RPM bounce up and down as it goes from 27 to 22 from 70-60mph below 60mph SA stays steady on both chips"

Please read the attached document, section: "Correction: ALDL Reporting of Spark Advance TDC (SA-TDC)"

There is an error in $8D OEM BIN. The SA-TDC reporting in DFCO is incorrect. You have to look at the SA-REF, which should be 0*. SA-TDC should report 0*+ initial timing. In OEM BIN it does not. In S_AUJP it does, because it has been corrected by its creator.