when i step on my gas pedal it goes an inch and a half in. what could be the problem?

Are you saying that it's not fully depressing? Check the simple stuff first...look underneath the pedal and around its pivot point. Floor mats and torn carpeting like to bunch up underneath it. Next check everything from the pedal to the firewall for anything that might be binding. Depress it with your hand and watch it. If you don't see anything on that end, pop the hood and find the cable going to the throttle. With the motor off obviously, put something down on the gas pedal that will hold it as far as it will go, and check the cable going to the throttle. The most obvious thing to look for under the hood is something preventing the throttle blade from rocking fully open. This could be a broken connector or a wiring bundle that slid underneath it... Look for any section of the cable that's split or coming apart, detached from any brackets that may be holding it in place, and also look for hard kinks in the sleeving around it as well. Then attempt to open the throttle further with your hand. If the throttle won't open to 100% by hand, then that's where your problem is. Also make sure the blade itself isn't sticking. With your weight off of the gas pedal, open and close the throttle blade by hand. It should be a quick, snappy motion with no sticking or binding anywhere in its travel. Gunk can build up around the throttle blade, especially on higher mileage engines, due to the PCV system recirculating oil vapors through the intake tract. If you suspect the blade itself is sticking, remove the intake tubing leading up to it and clean it carefully with a strong lint-free rag and a can of Throttle Body Cleaner. Don't use Carb Cleaner or anything else.

Could it be air flow?