So I filled up my 05 to head out for the weekend. I noticed my gas gauge wasn't moving and thought I was just getting good mileage. As I started to head back home, my gauge finally started moving. I was about 150 miles in by then. Today I was driving, and all of a sudden my car went to zero miles until empty. I put only half a tank worth in, and it says I'm full. Any suggestions? I know I could replace stepper motor. Seeing if there is a different option

 

Gas gauge level sensor is bad. Or the gauge is acting up.

 

Know how to fix cheapest way?

 

The dealer should have a test they can run to tell you. If Not the gauge is less than the sensor. The gas level sensor is inside the tank. That is a pain. See if anyone else chimes in that has had this issue. Seems like certain issues on the mustangs are common.

Here is another form talking about the same issue.
http://www.allfordmustangs.com/forum...ge-issues.html

 

Mine did the same thing years back, I believe there's a TSB for this. Apparently sulfer builds up around the sending unit in the tank and ruins it, was told to use a bottle of Techron every oil change, never had a problem since. Dealer fixed it under warranty at no cost. If you never used it, give it a shot..might be an easy fix and won't harm anything.

 

There is a vacuum line the connects the two tanks under your rear seats. When the main tank gets empty, the vacuum line sucks gas over to it from the other tank. If it is loose or loses the vacuum, it will cause the symptom you are describing. Get that checked first.

 

There are two tanks?? Always thought there was just one...

 

There should be one under each rear passenger seat. My problem was that I'd fill up, and shortly after getting past 1/2 tank, the gauge would drop to E and I'd get "0 Miles To Empty" just like what's happening to 05GT4.6.

The vacuum line between the tanks is supposed to suck/siphon gas from the other tank into the tank that's empty. That line was loose, resulting in no vacuum, so when the first tank went dry (shortly past the indication of 1/2 tank), the car thought I was completely empty. After fixing the vacuum line, I was good to go.

If you remove your rear passenger seat, you'll see that there is a fuel pump access panel under each seat for both tanks.

I'm 99.9% sure this is the OP's problem.

 

Just remove the seat and it is right there?

 

No, you need a lift and look between the tanks from underneath.

 

are you talking about the the fuel filter?
If you havent changed that in a long time, Id get that changed as well.

 

Try running a bottle of Techron in your gas first - some people have had success with this, especially when running cheep gas in their 'Stang.

 

Yeah, I will try this, and go ahead and replace the fuel filter. I live in San Angelo, Tx. There is something in the gas here haha. Do you wait to fill up to put that techron in, or did you just buy it and put it in?

 

Wait until the tank is almost empty then add a bottle then fill it up.

 

When I tried the fuel filter. It didn't work, next step is the techRon.

 

The fuel filter won't cause a gauge problem, give you bad gas mileage and make the car feel sluggish but that's all.. Try the Techron and if that doesn't help then might be the sending unit went south. When mine had problems, the gauge would read normal then all of a sudden drop to empty, gas light would come on then shoot to full then back to where it should be.. had the sending unit replaced and been perfect ever since. The Techron is good at keeping the sending unit clean of sulfer build-up which causes that issue. Just make sure you get the concentrate plus one and treats up to 20 gallons.

 

Thanks a bunch man! I'll let you know soon with the results. I finally put some exhaust on my car, so I'm flooring it more often and I'll have to fill up soon.

 

Sorry I’m a little late chiming in. My gas gauge did a similar thing about a year or so ago where it would get stuck at the halfway mark, but it only occurred during one tank fill. I had filled up at a place I don’t normally go and so it must’ve been cheap gas with more sulfur concentration. Took it to my trusted mechanic and he said the fuel sending unit is probably dirty from the crappy gas and so he added a little Seafoam fuel additive to the tank. The next morning, when I started it up, it did the trick and the fuel gauge was functioning normally again. I went out and topped off the tank at my usual place and, since then, it hasn’t had that issue anymore.

Hope your issue has been solved.

 

So far no luck. I did the royal purple additive and that hasn't helped. I just filled up yesterday and used Techron this time. Going to see how it will work. Even been trying different gas stations. More than likely it won't work though.