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Discussion Starter #1
I have a 02 mustang 3.8 and my mpg's are horrible .
Driving mix both city and highway and getting 16mpg ive replaced the fuel filter, wires, e3 plugs, and coil from american muscle
the car only has 55k on it for the year
air filter is clean/new, i did buy it used with 18' but i dont see it dropping the mpgs that much,

i work for a dealer ship and one of the lincoln techs did find a bad fuel pressure sensor, which i did replace with a ford part
any other help??
Thank you
 

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I was just reminded of this problem recently. Check your engine coolant temperature sensor. If the engine believes it is running cold it will enrich the mixture and kill your gas mileage. Good luck!
 

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Discussion Starter #3
I was just reminded of this problem recently. Check your engine coolant temperature sensor. If the engine believes it is running cold it will enrich the mixture and kill your gas mileage. Good luck!

if the engine temp sensor was bad or off would that affect the gauge or is that a seperate sensor?
 

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Just depends on your particular car. Some use a sender to the gage and some use the sensor for both.........
 

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As far as if the car is running rich, this could be because of a bad 02 or MAF sensor so check them. Next, fuel injector leaking can also cause a rich mixture. I would do a pressure test of the fuel system to make sure the integrity of the whole system is good. Any leak in a gas line or injector will show in a pressure test.

How about tire pressure? Incorrect tire pressure (too low) can cause you to lose a few mpg's.

How about spark plugs? A bad or heavily work spark plug could cause the poor gas mileage as the car will be suffering fro power loss and try to make up for it by sending more air and or fuel into the system.
 

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Honestly, a v6 in the heavy mustang will never get a good gas mileage. From factory they were estimated at 17mpg city. Especially if you have a lead foot that will drain your gas fast. So unless you increase your rwhp then your gas mileage will always be the same at 16mpg.
 

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I assume that you've done regular oil changes, and don't drive with low tire pressure? Those would be the obvious things. I've never used E3 spark plugs, but they've been renowned for misfiring/ not working correctly, so it is possible that you have a bit of unburned fuel. 16 pure city isn't that bad......if you drive a lot of highway miles and are still getting 16, then that is pretty bad.
 

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Discussion Starter #8
I assume that you've done regular oil changes, and don't drive with low tire pressure? Those would be the obvious things. I've never used E3 spark plugs, but they've been renowned for misfiring/ not working correctly, so it is possible that you have a bit of unburned fuel. 16 pure city isn't that bad......if you drive a lot of highway miles and are still getting 16, then that is pretty bad.

Getteing consistant poor mpg even on hyw tires are new& nitrogen filled,

checked the state of coolant temp sensor and indicates the car is running 210deg

and all the sensor values are with in spec, every car i ever owned used MAP this is my first MAF car so how do i clean the mass air flow sensor as was suggested?

the E3 were suggested by an american Muscle,
is there a better choice of plug?
i pulled some platinum plugs out before the E3's went in as a first step for this
 

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Discussion Starter #9
As far as if the car is running rich, this could be because of a bad 02 or MAF sensor so check them. Next, fuel injector leaking can also cause a rich mixture. I would do a pressure test of the fuel system to make sure the integrity of the whole system is good. Any leak in a gas line or injector will show in a pressure test.

How about tire pressure? Incorrect tire pressure (too low) can cause you to lose a few mpg's.

How about spark plugs? A bad or heavily work spark plug could cause the poor gas mileage as the car will be suffering fro power loss and try to make up for it by sending more air and or fuel into the system.
found a bad fuel pressure sensor because when we checked the fuel pressure it was 75psi at idl after repair back down to speck
 

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Discussion Starter #10
Fuel trims are good

fuel pressure around 65psi

o2s normal no intake or exhaust leaks

still getting 16mpg on hwy
 

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Put a normal set or autolites in there and see if that helps, many cars out there do not like E3's.
 

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Discussion Starter #12
put a normal set or autolites in there and see if that helps, many cars out there do not like e3's.
will try that but im leaning towards a bad 'maf" mileage actually got worse after cleaning it with mass airflow cleaner
 

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I assume that you've done your mileage check by filling up, then resetting your trip odometer, and then driving, and then filling up again and and then looking at the gallons to fill it (or litres) and dividing that by the miles or kms that is on your trip odometer? I ask, because some people gauge it on the fuel gauge, itself, and the 3rd quarter of the tank (on my car, anyways) plummets fast.

210 degrees temperature is alright for these cars, though if your car consistently runs those temps, it may be indicative of maybe needing to tune something up (coolant change, etc). Mine runs from 186-192 (though with heat reduction methods) in the hottest months of summer, venturing only past that for the odd peak at maybe 204 or so when there's extended idling.

Edit: just saw that you have 65 psi fuel pressure. This is way too high. It should be around the 40 psi mark. Could be a bad fuel pressure regulator, or something awry in the wiring of the fuel pump. Another guy on here had bought a Mustang with a fuel pump that was wired incorrectly, and it was running balls out all the time.
 
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+1 to ryan, with the engine running the fuel pressure should be at 25-40psi. With the key on engine off it should be 35-50psi. < Ford specs
 

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Discussion Starter #15
+1 to ryan, with the engine running the fuel pressure should be at 25-40psi. With the key on engine off it should be 35-50psi. < ford specs

atcually its running at 65psi and thats with a new pressure sensor, according to ford thats with in specs

and yess i gauge economy on miles driven devided by gallon's

185 miles
12.5 gallons
=14.8 mpg last fill up
 

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atcually its running at 65psi and thats with a new pressure sensor, according to ford thats with in specs

and yess i gauge economy on miles driven devided by gallon's

185 miles
12.5 gallons
=14.8 mpg last fill up
I don't know if the pressure is different on the 02's, but mine's a '99 and even on datalogs during regular driving, mine is at 40 psi on the fuel pressure, which is where all the Ford specs say that mine is supposed to be. 65 psi still sounds way too high.

Edit: did a search, and 40 psi was the normal psi, according to this source:

http://www.justanswer.com/ford/5dhh7-mustang-fuel-pressure-3-8l-40-psi.html

Found this (below) that states that fuel pressure shouldn't exceed 65 psi, but I can't find any info stating how long it should stay that way. I'm not the expert, but considering that my car is at 40 psi in regular driving, I can say that 65 psi should not be your normal psi for any length of time. If it is your normal psi for any length of time, that would explain the poor fuel mileage, and I wonder if you won't have fouled catalytic converters (and O2 sensors) soon from running extremely rich. The other thing is that if the pressure is that high, you're likely running a very rich air/ fuel mixture, which is also further killing your power, contributing to the poorer mileage as well.

http://www.allfordmustangs.com/foru...3-8-v6-fuel-rail-pressure-injector-specs.html
 

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25-40 is Ford Service manual spec for your engine running. 35-50 with the key on and engine off. I would look into your sensor being faulty since thats the only way it determines how much pressure it is in the rail. Are you using a computer or a fuel pressure gauge to determine your pressure?
 

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Discussion Starter #18
i don't know if the pressure is different on the 02's, but mine's a '99 and even on datalogs during regular driving, mine is at 40 psi on the fuel pressure, which is where all the ford specs say that mine is supposed to be. 65 psi still sounds way too high.

Edit: Did a search, and 40 psi was the normal psi, according to this source:

http://www.justanswer.com/ford/5dhh7-mustang-fuel-pressure-3-8l-40-psi.html

found this (below) that states that fuel pressure shouldn't exceed 65 psi, but i can't find any info stating how long it should stay that way. I'm not the expert, but considering that my car is at 40 psi in regular driving, i can say that 65 psi should not be your normal psi for any length of time. If it is your normal psi for any length of time, that would explain the poor fuel mileage, and i wonder if you won't have fouled catalytic converters (and o2 sensors) soon from running extremely rich. The other thing is that if the pressure is that high, you're likely running a very rich air/ fuel mixture, which is also further killing your power, contributing to the poorer mileage as well.

http://www.allfordmustangs.com/foru...3-8-v6-fuel-rail-pressure-injector-specs.html


contacted ford directly via the lincoln dealer i work at for the fuel pressure spec's for my year
 

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Whats weird is that I did the same thing as well. Although I looked at the manual myself and found the PSI was suppose to be 25-40 KOER. Try and see if you can look up the pressure yourself instead of calling someone else.
 

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Discussion Starter #20
whats weird is that i did the same thing as well. Although i looked at the manual myself and found the psi was suppose to be 25-40 koer. Try and see if you can look up the pressure yourself instead of calling someone else.
i did see it my self pressure, o2 trims, fuel trims, afr trims nothing spikes out of spec and was running in the shop for 40 minutes after the vehicle was at operating temp
both me and the tech could not definitly condem any perticular area
 
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