Nissan Repair: excess fuel burn, fuel pressure regulator, muffler replacement

Question
I have a 1995 Nissan pickup 2.4l auto. I cannot get it to get more than 20 mpg, and if the wind is in my face 15mpg. I have changed plugs,wires, cap, rotor, oil and filter, air filter,thermostat.Still thesame mpg.What do you suggest,injector flush? Also the check engine light is on

Answer
Bryan,

Depending on the gearing and tires you might be stuck there.  You can do some things to get better mileage like a K&N airfliter to free up the intake and a Magnaflow or Flowmaster for a muffler replacement.  Also, if your converter is getting plugged up a replacement would inscrease mileage.  If you have not replaced the oxygen sensor that would kill mileage due to it getting coated over the years.  They should be replaced every fifty-thousand miles but no one does.  Run the maximum pressure on the tires and make sure the brake pads and shoes are not dragging.  You can check the fuel pressure to make sure the fuel pressure regulator is not defective.  They fail open and that means too much pressure all the time.  Lastly, make sure the timing is set correctly.  For every degree of timing you get about a mile per gallon.  So, if your timing is set retarded the mileage will be less.  Make sure you do not advance the timing too much as that will cause pinging and that hurts the rod bearings as well as the mileage.  Set it to factory specifications and if it does not ping go up one degree at a time until it does.  Then, back it off a degree and that is the best you can get with the gas you are using.  For the check engine light go to Autozone or Checker and get the code read for free and correct that first.