check engine light

i flip the air cover over now the check engine light comes on and off when i play with the heat

year and engine size please

is it the 91' Camaro you have in your profile?? So im assuming its a tbi injection with the air cleaner lid?

If so, just run the codes and see what is being affected by flippin the lid over

year and engine size please
1991 305

Here is a link how to flash codes on pre 94 F-bodys
http://shbox.com/1/dlc2.jpg