just replaced the CTS with a new delco unit.

when engine warms up and goes CL seems to run idle/ nicely. WB shows toggle 14.4 to about 14.9 while cruising on xway for about 20 miles. when i exit xway and get slowed down in city traffic(prolonged idle sometimes) or multiple stops it seems the toggle goes lean 16 or 17/1 or greater with a low idle of 500 and then IAC takes over to keep commanded which is around 700 but with a bit of surge 500-800. i have not yet ran winALDL when this occurs but did log WB. when this occurs and i need to accellerate i get significant lean stumble and then AE alows me at accelerate abruptly as WB shows 12/1(AE). otherwise tip drivability seems pretty good until what i am thinking is maniflod gets fully heat soaked.
edit: maybe what i am seeing is the enleanment caused buy the IAC upping idle speed showing in WB the lean condition? i guess the 02 is just doing what it is designed to do. i think i will try setting commanded idle below 700 and then use throttle screw to set to 700 and confirm IAC steps are zero when engine CL ?????

 

Ron,

I assume your running C/L idle? What does your SA table look like? I've had symptoms very similar to this with new cam and I finally lowered timing in the idle area and rundown area taming the idle and helping to eliminate idle stumble and trailing throttle decel stumble.

 

at 400 rpms all map 4 deg total advance. 600 6 deg TA at all map, 800 rpms 8 deg TA all map, and 1000 10 deg TA all map. IOW at low rpm/ minimal SA all map. other SA rpms/map your tables. i believe this is what was suggested in an earlier thread i read? idle is somewhat improved over the SA you currenly run. that is the bin(yours or close to it) i ran up till this week when i made the changes in spark tables. i have little experience with my new setup. weather here was iffy past couple weeks. see my edit. i think it is idle speed/IAC/follower related. IAC is causing the lean condition? when weather improves will have more time to tune.

 

Similar symptoms I have had. Motor idled ok until temp got to 80c, then surge would begin. You may want to look at TF% and MAX TF Steps. I can't say that I am running idle SA as low as what you seem to be. Here's the SA table I just put together with a 10d Initial Advance. I haven't finalized timing for WOT just yet. I have kept the SA lower in WOT area since I was trying to tune VE at higher RPM/kPa areas and was not entering PE. I have been using the SA Slope constant to add more spark in the higher rpm areas so that I am at 36d TA by 5200rpm.