CTSv NEED HELP

[obd2]

CTS-V with 219/240-120lsa cam, ARH headers, ported blower, 90mmTB, 9.1/2.5 pulleys, Alky Control meth...just put it together, everything runs great except for when I'm completely off the throttle and coasting at which point the engine surges like it has a huge cam, even the slightest throttle input smooths things out perfectly.

The datalog says I'm jabbing the throttle rapidly approximately 19-25% (which obviously I am not) and the timing is jumping all over the place (like -10 to 45 degrees) as fast as lightening. Once the car has been driven for a while the problem clears itself up and everything works great, but turn the engine off for even a minute upon restart the problem resurfaces. I did swap the throttle body to no avail

[christopherstone]

Count me in because I might have similar mods in the future


Have you tried watching what cells you are in at coast..then smooth the AFR and timing in those cells?

I bet if you get the timing to stay still it will quit. Try using the VCM Controls to lock the timing advance at a certain number, log the timing again and see if its still jumpy. If it goes away then you know it is purely a timing issue.

IDK just to eliminate everything else?

[edcmat-l1]

Data log and tune.

[obd2]

I found the problem and taught it would be a good idea to post. I currently have an 2011 ctsv coupe with about 700 RWHP that I tuned using HP tuners. The afr are rock solid and throttle response is excellent. For the last week or so, a friend and I have been cloning his 2009 ctsv sedan to my 2011 ctsv.
The 2009 (Previously modded) and tuned by EFI Live, so I sucked the 2009 tune with HP Tuners and cloned it to mine. I noticed when performing a tune compare (once cloned) some tables would show-up as different, but when opened all numbers were identical. I install the tune and the 2009 ran fine with also solid AFR, but with some drivability issues. I then performed a completed re-write to help solve the issue but was unsuccessful. This problem was remedied by re-installing the factory stock tune using EFI LVE and modifying the stock tune via HP tuners. I have found compatibility issues between EFILIVE and HP tuners when trying to modify existing in car tune.
Hope this could help someone