Other than plugs with a distributor cap and rotor and plug wires, what else is typically done during an engine tune-up? I seem to be getting lousy gas mileage.

 

Make sure you get an "oem" style cap, If not they will give you one that has aluminum inserts that will corrode in no time.

 

Is your check engine lite on? Do a compression check, both dry and wet. If you have or can get your hands on a scanner that reads live data, hook 'er up. You're lookin' for 3 very important items. 1)fuel trims, they should read around 0 when the engine is at normal operating temp and at steady load, 2) your O2 sensor should be moving up n down, not steady, and 3) the temp of the coolant should be between 180 n 210...depending on the outside temp n whether or not you're using the A/C.
Also, take a look down the throttle body with the butterfly valves open. Is the floor of your intake plenum swimming in oil or just have a thin film? If it's covered in thick oil, your plenum gasket is blown. Last but not least,
pull your intake air temp sensor n clean it n reinstall it. AND...have the cat tested for clogging, any reputable muffler shop will do it for free.

 

BTW, what do you call "lousy" mileage?

 

Plenum been addressed? How old are your O2 sensors? (ok, 95, you only have one.) Air filter? Serpentine belt?

 

MPG is hard, we don't all drive the same, and have different types of roads and traffic. Does it take an hour to drive 7 miles to work or the store, or only 7 minutes? I live in Northern WI and don't have a garage, our truck idles a LOT this time of year and our MPG sucks. Also the fuel in winter seems a different blend that doesn't get as good MPG. So what kind of driving situation do you have, and what area of the country?

 

Make sure your air filter is clean and you aren't throwing any codes. There's not much to them other than that. BTW, I average about 12.6 in mixed driving and towing a small boat trailer. I rarely get much better than 13-14 even if I'm not towing, maybe 16 on the highway best case scenario.