08VRSS

I played around with the optimum spark tables for a few hours last night trying a few things. Getting the idle timing up around 20deg which has been said to be the best timing at idle for the LNF. This resulted in a very stable idle mostly, but idle hunting at stop lights this morning or under load with a/c on. I adjusted the optimum spark table a bit more (lower but still waaaay more than i had before) while getting gas this morning where I'm around 15deg at idle and the car really seems to like that.

So basically re-doing my optimum spark tables from scratch and adjusting base timing in those areas, I'm left with a very stable idle, and the cold start this morning was perfect, no issue at all and my fuel trims were absolutely awesome this morning. Still going to put on the new HPFP, but we'll see if readjusting the optimum spark tables were the fix.

08VRSS

Just to close this thread, the fix is the DAL table needs adjusted to adjust airflow at idle (2-5% throttle opening ideally) and the optimum spark table and ignition tables need adjusted to keep around 15-20deg of timing at idle. The DAL and spark tables both compliment each other and must be in tune with each other or else they fight each other and you get idle hunting or cold start issues. But, fixed.

If you need help with this, go over to hptuners.com forums and search. I read up on gmtech's (John) posts about adjusting this and it was the cure. DAL, optimum spark, and ignition timing.

Edit:

Also..... replacing the HPFP with a low mileage one from Mongorat427 stabilized the fuel trims very very significantly. I no longer get major swings on the STFT and the car is very easy to tune the MAF now that the trims are stabilized.

carterdillon004

I have 09 cobalt LT and it will be fine then all of a sudden while driving it will have total loss of power I'll have to pull over and shut it off when starting it back up it will back fire and won't want to stay running after awhile of this it will run fine for a little while then do it again. Also hard to start and rough idle with back fires and sputtering. I have noticed that when it's doing this it will bog down when pushing on gas then when I let off it will pick back up I have replaced fuel filter MAF sensor, MAP sensor timing sylinoids air filter when I replaced the MAF it seemed to fix it then after a week or so it was right back to doing it again