ok for like the last year ive been driving my truck (had for 9 yrs) it used to get 20mpg on average then i noticed one day it was just guzzling the gas its a 1993 4.9 5 speed no change in driving if anything i been driving it eeasier but i can drive as hard as i want now that im getting 7 mpg and it doesnt change. the truck doesnt run bad at all runs just like a new truck. ive replaced the plugs, plugwires, distributor cap, rotary button, map sensor, and changed oil. it has a k&n airfilter. ive ran code scans on it they all say maf sensor but my truck doesnt have one and it says it runs rich. ive cleaned o2 sensor and every time i take it out its white(doesnt that mean the motor is burning clean) and the timing is dead on. im stumped and my savings account from tax time is getting around $100 all of its went to gas just to make simple drives

 

Color of o2 really isn't an indicator, you can test the o2 with a torch and multimeter. What code is it throwing (173)?

 

Read the post at the top (by just call me Sean) about checking OBD1 codes and check them that way.
Running rich would cause excess fuel consumption. Lots of things could cause it to run rich - even a little sensor (that costs less than a tank of gas).
Learn how to read the codes from the check engine light and that should help narrow things down a little.

 

Check your oil. See if the level has gone up at all and see if it has a gas smell. A drop the significant could be the culprit of a leaking injector. It'll cause the oil to thin which can cause the engine to work harder, in turn causing mileage to go down. Also, once you shut it off the pressure will will just leak raw fuel from the injector. This in turn can mess with the o2 sensor causing it to possibly read wrong and cause even more mpg robbing problems.

 

Your engine may be showing a cold reading on the sensor from either a bad sensor or your engine is really running cool. I would check the cooling system and the cooling system sensor.

 

56 55 65 72 18 are all the codes but 2 or 3 of these have been on the truck since i got it 9 years ago could any of those codes make a difference that big in gas mileage i have a code scanner and have scanned this truck millions of times this week because buying obvious things quit workin...im 16 and me or my dad can figure this out and my dad used to build motors all the time

 

my truck has always ran pretty cold i live in north ga and when its around 40degrees out it barely moves off c but during summer it runs almost halfway unless your in traffic about 5 min of idling in a traffic jam and itll heat up pretty good but down here we dont have very bad traffic so thats not causing it

 

first of all 93's have 3 digit codes.

 

i thought they had 2 didgit because here a few months ago the map sensor went out and the truck would start and stall it gave a 2 didgit code and it said map sensor and that fixed it. ill run another scan in the mornin and update this with 3 didgit codes and see what we got then

 

yeah 92-95 was 3 digits, 87-91 is 2, and 96+ have 4 digit OBD11 codes