ya I have some more info when i start my car after a few hrs it blows out black gray smoke and it smells like gas. What can this mean?

 

Get your injectors NOID tested... Any codes/SES light?

 

no check engine light but can i still scan. and how do i get it noid tested

 

pick up a noid test light at the local parts store. u plug it into your injector wire and if the computer is telling the injector to fire it will blink.

 

Hi I solved the back firing problem, it it was my spark plugs lol . I am not sure if it solved my mpg problem. I has not tested it yet. I had another question to ask, what controls the radiator fan? my fan never comes on i have replaced the relay but it still wold not come on.

 

the ecm turns the fans on. the temp sensor tells the computer what the temp is. if u unplug temp sensor the fans should come on. if not the fans have a wiring problem or the fan is failing.