10MPG!!! whats wrong??

jstang209

Dirt-Old 20+Year Member
Jun 3, 2004
640
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Stockton 209
hey i just got a tune-up on my car.. new rotor, cap, wires, plugs, and fuel filter.. and this is the gas milage that im recieving... the only things i havent changed yet was the pcv valve and someone mentioned o2 sensors, but if both of those are bad will is cause 10 mpg.. i mean my car is a 4cyl.. someone help me out becuase this is really hurting my wallet! thanks
 
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jstang209 said:
hey i just got a tune-up on my car.. new rotor, cap, wires, plugs, and fuel filter.. and this is the gas milage that im recieving... the only things i havent changed yet was the pcv valve and someone mentioned o2 sensors, but if both of those are bad will is cause 10 mpg.. i mean my car is a 4cyl.. someone help me out becuase this is really hurting my wallet! thanks

It sounds to me like you've mistaken your 5.0 for a four banger. Just kidding. It very well could be the o2 sensors. if not that then it could be your timing. My timing was messed up and it screwed up my gas mileage.
 
Dan P. said:
Check the inertia fuel switch thats in the back. Should be behind a rubber boot.
Dan

can i get a little more detail onwhere the inertia fuel switch is and what to do with it.. and my car never did this befor, so can the timing get messed up out the blue? what is it supposed to be set to
 
10 mpg seems like quite a significant symptom. Just off the top of my head, it sounds like a "closed loop" running engine. Could be the o2 sensors, but they don't usually go bad together all at once. Has the mileage been getting worse and worse or is this the first time you've checked it in a while?
 
I've heard of the timing just going bad, but that wasnt the case with me. If it's just a matter of adjusting the timing it shouldnt be a huge problem. If it's something with the timing belt or chain (whatever the case is) it'll most likely be a pain in the ass. I'm not sure what the timing is supposed to be set at, but i know that the timing on mine was bad when I got it...it just steadily grew worse. For the inertia fuel switch, Look behind the plasticky carpeted walls of your trunk (thats where it is in my notchback, i dont know about a fastback) and it should be on the left side. It's a little gray box with a button on the top and plug in the bottom
 
all the fuel switch dose, is if you in a car accident for say, and you stop really fast, it cuts the fuel pump, so that if a fuel line is broken some place from the accident, it dosen't pump gas all over the place and start a fire.

again, the best words of advice, are pull the codes. That will at least give you a starting point.
 
its been getting worse and worse, the only other thing i notice to is a loss in power when i turn corners(in 2nd gear) its like when i hit the gas it seems like it not doing anything.. not like hitting the gas in nuetral but i feel acceleration but not a normal acceleration.. i dont know if that makes any sense to you guys but yea.. thanks
 
freakintiger said:
Correct me if I am wrong, but what does the inertia switch have to do with gas mileage? I've always understood that I.S. tripped= no gas=no start. Reset set it (push the red button)and all is well again. :shrug:
You are correct there is no way the the inertia fuel switch will be the problem
 
Fuel pump is in the tank...it can only dump fuel back into the tank.

We only have one 02 sensor...if you know how to loosen and tighten a single nut or bolt, you can do it.

You need to scan for codes first and foremost, then check the fuel pressure (or pull the vacuum line off the regulator and see if there is any gas in it).