1. My miles per gallon is roughly like 17 and i have stock tires. i just replaced my fuel filter, did a rotor, distributor cap, plugs, wires, oil change on her. and im getting this horrible milage on stock tires. any ideas what's going wrong?
1. Check that the engine is in good tune. (You've tuned it up, but check things like low compression, etc.)
2. Check that all your smog stuff is working properly. i.e. Various sensors can enrichen the mix. Better performance, bad MPG. Oh, and below 40 degrees, your rig will get worse mileage... maybe 10-15% worse. It's just a 'Zuki thing.
3. Check nothing is dragging. That bang could be your rear brake shoes locking, for example. When it's cold, lift each wheel and see if it spins reasonably freely. A sticking front caliper was costing me 4MPG.
4. Check your odometer? My neighbor put on oversized tires then claimed his mileage sucked. It turns out he was going about 10% further than the odo showed... so mileage wasn't as bad as he thought.
5. If you trust her, try a long distance run. Running well, you should see about 24-30MPG over 50+ miles of running, if all is right. (This gives her a chance to balance her temp & such.) It wouldn't hurt to dump in a can of injector cleaner. Some of these rigs have idled around town & need an occasional trip to blow things out.
6. Mud slinger tires and lifting the truck will hurt your mileage... but it's a decent enough trade.