My trialblazer is using up gas but already had a tune up and nothing is leaking

possible air leak in the hose to the computer

my locks did the same thing I disconnected the car battery for 15 minutes and it reset them.

Getting a smoke test is the right direction to go in.
The computer vents the gas tank to the vapor canister while the engine is running. It also pressure tests the system for leaks. Some where between the gas tank and the vapor canister there may be a leaking hose or valve. Or it could be the gasket on top of the tank where the pump assembly went in.
The gas cap could have been a source for the leak, the other things are not involved.

I'm unsure, it sounds more like a vacuum leak.

Might need a good tune up, MAF mass air flow sensor, air filter, fuel filter, there might be a vacume leak. I would have suspected the IAC but you have already replaced that.

Thanks for choosing FixYa and welcome. You may want to try a fuel cleaner and changing the fuel filter first if you haven't already. Check for any codes that may have came up if the check engine light is on. Check all your fuel lines and gas tank again. You may have a bad fuel injector so check them for sure. If one is leaking, fuel can be smelled. A simple tune up can help your gas mileage, as well as the cleaner. Check around the fuel filter for loose hoses. If you can access the fuel pump from your back seat, check in that area also. Check the engine block for leaks. Remember, if it is leaking there, the gas will evaporate before you notice leaking spots. Check all your lines behind the engine block and at the firewall. Are your rpm's jumping any? High idle? The throttle may need adjusted. You may be getting rich fuel as well. Check your catylactic convertor. There may be a leak around the fuel pump so that is an option also. If it is not in the back seat, you will have to pull the tank to check it though.

Fix the smell first, as you are a fire/explosion hazard. Look for wet spots, but something, somewhere is leaking. Inspect the evaporative recovery system and all hoses. When this is resolved, look after the rough running on acceleration.

most likely cause spark plug wire bad, or you got them incorect when you did a tune up if it happened before tune up. swap the wires but keep the fire order the same . if the wires are good then the # 4 should still be the problem . put them back the way they were now you have ruled out the wires next check the fuel injetion system check for a vacum leak around the # 4 injector listen with a lenght of hose . listen to the injectors they should all be making a clicking noise.cant help you more then that. make and model would help the next expert wiz or guru

if its dripping out the end of the exhaust its probably just water, nothing to worry about.

usualy it is 20 miles to the gallon and to improve your gas mileage i would do a tune up... spark plugs, wires, cap, rotor, fuel filter. and add tune up in a can its only like $4.00 from autozone. and also replace your airfilter, add air to your tires like 35 psi. and clean your fuel system .