Hi, just a strange thing and wondering if someone else has noticed this...

I've fueled my car with Shell Vpower 91 for as long as I had the car, and it seems to be working at its best when the gas tank is full. No stumbling, just smooth power, quick response. However, when the gas tank is low, I get minor stumbling, not unlike the "hesitation", far less severe but still annoying and that makes my car hard to drive smoothly in trafic.

I am going to the dealership next week, I will talk about the fuel pump TSB... Do you think my problem could be related ?

Many thanks

 

I've never noticed any problem like you are describing. I do have the hesitation as per the TSB, but that only occurs after a long cruise, and I get hard into the gas.

Why are you using 91 octane gas? Unless you have a tune on your car, you are wasting money. Infact, without a tune (stock setup) your car will run better on 87.

 

RottenRonny is correct. Your Mustang is specifically tuned to run on 87 octane. Unless you have CAI or some other performance speciality re-tune you really should not use 91 octane.

Fuel Quality is specified on page 232 in the 2007 owners manual. Probably the same page in the previous years as well. But it mentions some of the symptoms you describe are due to running "Premium" fuel like 91 octane.

 

It would make sense if car was always running roughly, but it is fine with a full tank of gas. I am running a Steeda CAI & SCT tune, that's why I run 91.

Thanks for the tip for the owner's manual. We, 2005 owners do not have this chapter !

 

Every car I have ever owned (which is not many, 3 maybe) always ran "better" on full tank of gas. Placebo? Maybe...gas degrading slightly in the tank? Maybe...who knows?

 

If you haven't taken care of the TSB for the fuel pump, doing so might take away your probs! That's for 05's as well right?

 

I've experienced this with all the SEFI Mustangs I've had. It seems theres better fuel pressure to be had with a more full tank. I honestly don't notice it as it drains, but when you put at least 1/2 a tank in when it's empty you definitely feel a little something extra.

 

So to use that NOS product with a 7 point increase is bad then ? fuel additive.

 

Well, the car goes in the shop next week for the TSB... I will post findings here !

 

What's the tsb # for the fuel pump problem ?

 

tsb 06-9-9

 

I havent had any problems with my 05 , guess I might be the lucky onee . Of course with only 6000 miles I better knock on wood

 

Fuel pressure greatly affects performance. A full tank of gas generates "head" pressure which assists your fuel pump. If the tank is lower, then so is the head pressure, and the fuel pump needs to work harder to generate the same amount of flow to the engine. It has always been a balance between the added weight of more fuel and the increased performance from more fuel pressure.

The TSB should help as Ford will put a new fuel pump in your vehicle. I noticed more fuel pressure off the line with the new pump after my swap was done.

I really have to commend Ford for standing behind everything on this vehicle. From what I have seen and heard, everyone is being taking care of in a professional and fair manner.

 

Ok I don't see a TSB for 06-09-09 where is it?

 

If your past your warranty mileage are you still eligible for these TSB's?

 

If you use 87 Octane the car will run better. 87 Octane is recommended for the V6. Changing the fuel filter after 20,000 miles helps also. Every four months you should add a container of Chevron Techron to the gas tank, perferably when the tank is on low so when you fill up the fuel will dilute the Techron product for smoother flow through the fuel injection system.

 

Well, the TSB fixed my car

It really seems like the bad pump was starving my car in fuel... Now the car is smoooth and makes more power than before, with way improved throttle response. It also idles smoother. I'd say this is a must do if you think your car has any kind of stumbling