I am dismantling a tune in a 05' C6. The car is a H/C car that was tuned a couple years ago by another shop. We just did a couple minor upgrades so the car is back in our shop. The car has always had an odd idle in which the car rocks from side to side (and its not the cam). While logging data I noticed the timing is oscilating between -5 to 23 degrees and the rocking follows the timing swing.
I noticed that the the base timing table for idle had 13 in the heart of the idle area and the high and low octane tables where in the mid 20's. We went and bumped the idle base timing to 18 and it seemed to clean it up a bit but was still pretty erratic. I started snooping around the spark tables and couldn't find anything that looked like it would command these values or modify the base timing. What I did find was B5132 for idle limit. The value was -7. For the hell of it I changed it to 18. Once the car was started the timing didn't budge from 18 and the car idled very stable. It did however raise the idle from the desired 900 to about 1050.
Just starting to get into the LS2's and not sure of what else in these new tables effects the final timing value. I did also check the idle overspeed corrections which are at 1.00.
Any thoughts? I ran out of time tonight to keep playing so I though I'd throw it out there!
Thanks
Howard