AFR ?? Help Rich AS hell????
 

I had my car tuned about 2 months ago(hp tuner tune ) car ran great until I ran a tank of 100 octane unleaded i ran through the whole tank then filled up with 93 afr was 11.5-11.9 now 10.0-10.5 wtf only other change is a kn typhoon intake no cel just confused at this point do i nned to reset the pcm or get it retuned ????

hmmm only thing I can think of is maybe the fuel trims relearned themselfs on the 100 octane and now they have to relearn them back. Run through this tank and then see what the next will do. Maybe someone else can chime in if they know something better.

Bump for you.

Was the car tuned on 93? If so....why did you run 100 thru it? Without being tuned for 100 octane you'd be seeing minimal gains so there was really no point...

Bored or Nitrous maybe?

Also, depending on what model cobalt the OP has, and provided I'm not wrong...pre 08 models don't have any sort of learn down feature or anything like that. If anything, this sounds completely ass backwards. I could possibly be wrong on this as well, but running 100 octane on a 93 tune would cause you to be rich as hell.

Since its posted in the lsj section im going to guess he has a 05-07 ss/sc cobalt.

You can guess that all you want, but I've seen I don't know how many noobs post in this thread about their 2.2's or 2.4's lol

I would guess that you need your MAF retuned since you swapped the intake. I could see the car running slightly rich for a short bit after switching from 100 to 93 while the fuel trims adjust, but nomore than 100 miles.

Finally...someone who knows what they're talking about lol

2007 ss/sc
 

To add to the confusion the car is a 2007 ss/sc and was tuned on 93 ran the 100 beacause I added a h/e and for no apperant reason thought it was a good idea :( took half the tank to bleed the air out of the system thought it would cause less issues ..