Can a car be throwing codes with no check engine light?

[MustangLife]

My cars running rich on the dynojet, but I have a dyno tune on a mustang dyno. Which it is suppost to be lean. Can I go to Autozone and have the codes checked. I have no check engine light, but the car just doesn't seem normal to me. I also lost 10 rwhp and 15 rwtq from the other day compared to about 6 weeks ago.

Thanks
Josh

 

[Jr2fast]

get it leaned out some more. I am no expert but it sounds like your computer learned the new a/f ratio and adjusted for it

 

[MustangLife]

I didn't know the computer can adjust to what a piggy back chip did to it. Can anyone else clarify this.

Josh

 

[mogs01gt]

The problem is the two different type of Dynos. You need to go back to the same dyno each time to get a good comparison on the mods you have done. Going back to two different dyno's is not how you want to compare dyno sheets and/or air/fuel charts.


Stick to one shop.
Nick