944withnos

I'm not familiar with the Mustangs FI system so I'm here to learn about what you find out... But what I'm saying is if your air/fuel ratio is "#"% from the stoichiometric ratio (or what Ford thinks is the 5.0's optimal ratio) and it is not running optimally then you have a reason to complain. Normally I would think the FI system would adjust fuel depending on your air density (if your air is rich with oxygen then you'd need more fuel to achieve stoichiometric-or ideal burn ratio). Ford can only give you a baseline map (to cover the entire US) but areas like Colorado would need a correction for fuel (if the base map was made in Orlando). The oxygen sensor is used in a closed loop system to give feedback to your FI to tell it to give or take fuel. So if the number you are talking about is a 13% addition of fuel to the baseline map I would think this is normal and the O2 sensor is giving feedback (or you would be running 0% and running poorly for your area).
If you were to get a tune...then you would most likely fatten the fuel mixture and your "baseline-tuned map" would then be considered 0% (or 13% more fuel than OEM map) for your area at current conditions until conditions change.
Maybe Ford releases different maps for different areas of the country? For example - Could you have a car purchased originally at 5000 ft above sea level and you live at sea level? Just taking a stab... Let me know what you find out!

texastboneking

You are not actually running lean. Your computer is adjusting the ratio 10% to keep it from being lean. So your still in the correct mixture. Its just the computer is having to adjust 10% off factory programming to maintain that correct mixture

texastboneking

Don't pay attention to short term trims. Pay attention to long term trims. Short term adjust too quickly to be able to judge the computer compensation

holtywsp

Thanks. I'm just gonna tune it and go. It will be fine. Thanks again for all the comments.

texastboneking

No problem buddy!

holtywsp

Bump. Back again with a update. Car is showing +24% in the long term fuel trim and no light on still. Why not?

holtywsp

Gas miles have been steady on the decline for a month and a half. Prob bc its running super rich. Vacuum leak? Or what else could do this? Bad upstream o2 sensor not getting air/fuel mixture right

holtywsp

Update. Got new tune from steeda yesterday and got it loaded in the car and she is a completely diff car. Pulls like crazy. Guess the tune I got first was a bit on the rich side. Got 26.4 mpg on the way to work this morning going 85. I haven't seen the on board computer ever get that high. Gonna keep an eye on it for the next few weeks but I can tell already that its a completely diff acting car now. For the better. Guess I need to make sure my 91 octane tune wasn't doing the same thing this 87 tune was doing and running very rich. But with gas in Nashville for 93 at $4.20 a gallon it will be a little bit before I check it.

Bucko

Is this a V6 you're "tuning"? And what about warranty? I've heard that the Ford techs can tell if a tune has been installed, even when it's flashed back to stock before a warranty visit. Is this true? If a tune is installed, does this void any warranty issues on the drive train?

I see that TexasboneKing has been responding with good info; just curious on Ford's stand on custome tunes while a warranty is on the car.

I've been seeing the same MPG on my stock tune (2011 V6) cruising between 80 and 90 MPH on the early morning freeways; about a 190 round trip each day.

holtywsp

Nope. 5.0 v8 getting 26mpg with 3.73 gears. Tuned by steeda. No #8 problems out of there tunes. And yes ford can tell on the '11-13 if they have been tuned no matter if u return it to stock or not. But some dealers look past mods. Just got to find one that does.

2011_STANG_GT

How many times do u have to ask this question? You know Ford will look at any way to void the warranty if the tune is the EXACT cause of the failure. A reputable tuner such as AM (BAMA) or Steeda are very safe tunes. How many of these so call "failures" have you actually come across from the THOUSANDS of people that are running tunes.

RISK IT FOR A BISCUIT or keep it plain ol stock, its that simple.

texastboneking

yes they can tell... but few techs actually check for the tunes now... the computer doesn't check itself. The tech has to go check for it. So as long as your not an *** when you go in and you don't mention the tune you most likely wont get checked for it. Expecially on the v6. The v8 is the one with the warning tsb.

Bucko

I only asked once....