Help!! Terrible Gas Mileage on my sone 1999 V6 Mustang.
03-15-2015, 11:53 AM
#1
Thread Starter
Join Date: Mar 2015
Location: Ca
Posts: 11
Help!! Terrible Gas Mileage on my sone 1999 V6 Mustang.
I just got my son a 1999 V6 Mustang (90,308) for my son, My sister gave me the car and I shipped it from NJ to Ca. (it's passed Smog) We filled up the tank drove the car and we are only getting 160 miles to the tank, that equals out to about 10.6 mpg. So I took it to the shop, and changed wires, spark Plugs (Autolight Uridium), Air filter, and yes the Fuel Filter was changed. Hoping this would fix the problem. Still getting the same mileage out of the vehicle about 160 to the tank. When I first bought the car I dove it through the first tank of gas for safety purposes, (I'm no lead foot) wanted to make sure the car was safe for my son so drove it around for it first full tank, 160 to the Tank. I've been reading the threads and no one has yet posted what is causing the problem, I just see people saying tune up (Plugs/wires filters etc) I'm sure or hope that there is someone out there that has finally diagnosed this problem I've seen it posted on many sites but have yet read what's the actual problem, PLEASE HELP!! 
When I go back to the station to fill up on gas (When the light comes on) I'm adding about 13 gallons of fuel so I do not have a faulty gauge I believe it's reading pretty accurately. I bought some new 02 sensors 3 to be exact, haven't put them on yet for if it's something else I will return them back to the store. I don't wanna put too much into the car but bad gas mileage and money spent into the car from gas could have fixed my problem So it would be foolish to ignore it.
When I go back to the station to fill up on gas (When the light comes on) I'm adding about 13 gallons of fuel so I do not have a faulty gauge I believe it's reading pretty accurately. I bought some new 02 sensors 3 to be exact, haven't put them on yet for if it's something else I will return them back to the store. I don't wanna put too much into the car but bad gas mileage and money spent into the car from gas could have fixed my problem So it would be foolish to ignore it.
03-16-2015, 08:10 AM
#5
1st Gear Member
Join Date: Aug 2014
Location: New Jersey
Posts: 80
As stated above, definately check the brakes especially the E-Brake operation. These tend to freeze up especially on an older car that's seen it's share of winters on the east coast.
What size tires/wheels?
-This would be detrimental as these cars have electronic speedo and if the car is running taller or shorter tires (overall diameter) than stock it will throw off the speedo and odo readings. And speaking of tires, how are they? Good air pressure and even tread?
If the car runs fine, no CEL and doesn't smell like it's running super rich it would narrow this down to chassis/susp/drivetrain.
What size tires/wheels?
-This would be detrimental as these cars have electronic speedo and if the car is running taller or shorter tires (overall diameter) than stock it will throw off the speedo and odo readings. And speaking of tires, how are they? Good air pressure and even tread?
If the car runs fine, no CEL and doesn't smell like it's running super rich it would narrow this down to chassis/susp/drivetrain.
03-16-2015, 09:19 AM
#7
Thread Starter
Join Date: Mar 2015
Location: Ca
Posts: 11
Had the brakes done, new calipers on the front, car rolls smoothly. Transmission fluid changed and looked over. I've seen threads with my same exact problem but no one has yet posted what the problem was and what they did to fix it. Tuned car, changed air and gas filters, checked for Manifold leaks, ran 3 bottles of lucas gas treatment (Yes on 3 different fill ups, lol) I remember someone saying something about a fuel injector might be sticking in the open position. I'll check that out. I bought 3 new O2 sensors, I'll put them in I guess, it can't hurt. it's now becoming a money issue, great running car but for my son to get back and forth to school it's going to kill his wallet so it's something I must get fixed. with the amount he's going to spend in gas it's would be stupid of me not to find the problem.
03-16-2015, 10:06 AM
#8
5th Gear Member
Join Date: Mar 2008
Location: Clermont, FL
Posts: 2,952
Since you said the car runs great with no CEL, or smell of gas, then nothing related to sensors or run by the ECU will help it. It has to be something in relation to rolling friction.
My money is on the rear caliper mounting bracket pins.
New calipers wont fix the problem. These are on the mounting bracket itself.
IF you can get them removed, they need to be sanded down and a liberal amount of high temp grease applied.
My money is on the rear caliper mounting bracket pins.
New calipers wont fix the problem. These are on the mounting bracket itself.
IF you can get them removed, they need to be sanded down and a liberal amount of high temp grease applied.
Last edited by PNYXPRESS; 03-16-2015 at 10:08 AM.
03-16-2015, 10:58 AM
#9
Thread Starter
Join Date: Mar 2015
Location: Ca
Posts: 11
The car rolls freely so I do not believe I have a friction issue, I'm not sure of the O2 sensors as of yet, I haven't replaced them, I'm going to do it this week. BUT if someone knew of anything else, I would look into that because I'm not getting a Check Engine light for my O2 Sensors. So I doubt that's the issue BUT I spoke to a mechanic and he said that his next step would be the O2 Sensors.
03-16-2015, 03:21 PM
#10
3rd Gear Member
Join Date: Apr 2011
Location: Wisconsin
Posts: 917
Does this car have a tune? It sounds like it may have the O2 sensors turned off.
I'd go back to basics...pull and read the spark plugs, check vacuum,compression and timing. If you have access to an exhaust gas analyzer that may tell you more.
I'd go back to basics...pull and read the spark plugs, check vacuum,compression and timing. If you have access to an exhaust gas analyzer that may tell you more.