kclivie

I have a 1987 chevy camaro with tpi 350 my problem is i get the codes 23 and 42 code 42 states that it an EST problem can anyone tell me whats this is and 23 states M/C solenoid circuit i need to know what these do and where are they located on the car. the car runs but back fires idle good bu when i give it gas thats when it starts.