really bad feul mileage?

[Mustang5L5]

but usually if theres no light theres no code.

That's not true with OBD-1/EEC-IV

Of the 99 or so possible codes, only 13 trip the light.

 

[red-fox]

ok, I did see the light flash but I wasn't really paying attention to it so I'm not sure if it flashed twice but it did flash.

 

[Mustang5L5]

operating temp engine off but key was on

You need to do the codes with the key off, and then a second time with the key on. That will test the engine running codes and things like EGR, and o2 sensors.

These cars aren't like newer OBD2 cars. There are actually 3 different sets of codes to read. Key on, engine off, continuous memory, and then key on, engine running codes.

You need to get three 11 codes to be considered a pass

 

[red-fox]

Ok, weekends pretty busy but I'll do some more scanning when I have time with key on and off and will watch for the code 11. thanks for all the help!