So my civic has been getting really crappy gas millage. Like that between 16-18mpg. which I'm pretty sure is terrible for 1990 civic. I don't understand why so if anyone could maybe give me some reasons why it might be getting bad millage I would appreciate it. I've already checked the tire pressure and theyr all good.

 

Could be MANY things. Look at general maintenance first.

Are the spark plugs good? Have they been replaced lately? Have the plug wires been replaced lately? Fuel filter? Air filter? Have you run a bottle of injector cleaner through the gas tank?

Do you have a DPFI or MPFI engine?

 

its DPFI and the spark plugs and wires were put in 5-6months ago...not so sure about the air filter but i think it might need to be replaced and i might go check the fuel filter and a bottle of injector cleaner wont hurt.

also, there is a hole in the air chamber..could that cause any problems?