2009 CTS-V has TM Advance spark jumping aggresively on decel causing surging

[Snowman1987]

Yes, I will post a log soon.


This is a new one.

2009 CTS-v
Small cam
LT headers
Aggressive pulley setup.

The issue is on decel it sometimes gets in a strange decel surge thing. In the log you can see the TM spark jumping crazy.


I have tried lowering base air, lowering and raising Minimum Tm spark to compensate/offset it, but nothing seems to totally get rid of it. Not seen this one before......

About 23 seconds in you can see it start to jump..... On this log, that is the only time it did it.


Thank you

[hjtrbo]

Add spark, fuel and ETC torque management types into your scan list. Will help narrow it down.

[PGA2B]

Not sure if it matters, but the fuel pressure is all over the place. Mine is a pretty steady 50-51psi unless in WOT.

[Snowman1987]

I did. It shows ETC type drag and Spark type TCS. Disabled TCS, no real difference.


PGA2B. It seems like the 09s request a lower amount of FP during low volume needs than the later years after comparing a few of them last week when noticing the same thing...version 21.hpl

[PGA2B]

Interesting to know! Thanks for that info! I'm only a hobby tuner...

[Snowman1987]

Interesting to know! Thanks for that info! I'm only a hobby tuner...

It doesn't matter! Everyone is learning all of the time when tuning.

[hjtrbo]

What happens when tcs is turned off via the button on the dash? Same thing?

[Snowman1987]

That is one thing I haven't tried! I will this afternoon. I have been taking a break from it and working on different projects. You know how it is when you have an issue that just doesn't make sense.... Especially since I've done many other Vs without issue.

Thank you for the followup and I'll report back soon!

[Alvin]

Can you try to go back to your stock idle base and coast down spark tables.. I can't say for certain that they are a problem. But they look like they may cause other issues.

Also, I'd try putting the fast torque exit stuff back. as a trail. Most automatics drive better with this on.

[hjtrbo]

Another thing to try is max out everything on the ecm torque management tab.

[hjtrbo]

This is interesting....
https://www.freepatentsonline.com/7306542.html

[Snowman1987]

FWIW, I did that (spark tables) as a test. I put it back with a tune that was closer to what it came off of the dyno with and, of course it did it, until I clicked the TCS button and it immediately stopped! NOTE: Once clicked once (whether on or off it seems to never do it again.................)

In this log, you can see after the first small acceleration, it does it, and I click the TCS button while it is doing it and it stopped immediately and never does it again.


You can disregard the end as I was just confirming a misfire as well to look at next. The car has 28s on the rear and 26.5 on the front, not sure if that is the issue or not.


Current tune and log coming.fixed.hplversion 23 misfire on.hpt

[hjtrbo]

Likely something going on in the background that we haven't got mapped to us yet. .

[Alvin]

FWIW, I did that (spark tables) as a test. I put it back with a tune that was closer to what it came off of the dyno with and, of course it did it, until I clicked the TCS button and it immediately stopped! NOTE: Once clicked once (whether on or off it seems to never do it again.................)

In this log, you can see after the first small acceleration, it does it, and I click the TCS button while it is doing it and it stopped immediately and never does it again.


You can disregard the end as I was just confirming a misfire as well to look at next. The car has 28s on the rear and 26.5 on the front, not sure if that is the issue or not.


Current tune and log coming.fixed.hplversion 23 misfire on.hpt

The tire size thing might be a issue. I had weird TM stuff happening on a C7 and it came down to miss matched tires. But I've never seen a gen 4 act that way.

[Snowman1987]

The tire size thing might be a issue. I had weird TM stuff happening on a C7 and it came down to miss matched tires. But I've never seen a gen 4 act that way.

Thank you... Also, I corrected the fast torque exit back to stock as well.

FWIW, I've never sen this on a gen 4 either!?

[Snowman1987]

Yes. I assume that to be the cause as well.

Now it is time to get more pump to this thing and see if we can get it dialed in!

[hjtrbo]

Did you solve it with tyre size correction?

[Snowman1987]

He normally runs the same size tires front and rear, so to avoid this with the street tires, we decided to not mess with it. If he decides to run these full time I will configure them and see, so the short answer is not yet 100% determined...