Horrible gas mileage whats the cause?

Jester73440 · Sep 2, 2005

I have a 96' ford thundebird with the 4.6. And my gas mileage is horrible sometihng like 13mpg city/highway average. Its been bad for a while but with the prices going up I need to make an adjustment. I know I'm not going to get great mileage but I checked the .gov site and i should get 18 city 24hw. So today I checked for brake drag and everything is fine. My trans is shifting fine. And no I don't drive like and ass nor Am I towing a boat. I'm getting no codes and the car drives pretty smooth. I think it started when I did the spark plugs I found out I gapped them wrong so I redid it and ever since then its been a pig. The plugs have about 30k on them the car has 89k on it. I'm going to pull the plugs tomorrow and take a look at them. but any advice will help because I'm stumpped here. Whats a good plug/gap to throw in this car anyway?
thanks

blackink00 · Sep 2, 2005

have you changed the fuel filter in a while? also how is your air filter? and just stop mashing the gas

Jester73440 · Sep 2, 2005

blackink00 said:
have you changed the fuel filter in a while? also how is your air filter? and just stop mashing the gas

fuel filter no i haven't changed it. air filter is a k&n and its clean and I don't smash it

sgarlic · Sep 2, 2005

Don't feel bad. My '04 has gotten 12mpg since the day I drove it off the lot, mashing, not mashing, a/c on or off, shifting at all different rpm's.

MEAN03GT · Sep 2, 2005

Theres somethign wrong with your car then, dont tell him not to feel bad, why dont you go fix your ****, 12mpg is either because you have a heavy foot, or your car is ****ed up.

So go have it checked, change the fuel filter, and make sure everything is fine, then try to ease on the throttle and drive slow.

sgarlic · Sep 2, 2005

Nope, it's not a heavy foot, and my car isn't ****ed up. It's brand new. I have 7000 miles on it. Done nothing but exhaust and shifter.

Got 12mpg off the lot with zero mods, 20 something on the highway. It's called piss-poor tuning by Ford.

And who the HELL buys a Mustang to drive the car like a grandmother? If you're concerned about mileage, don't buy a Mustang.

Project89 · Sep 2, 2005

I would change the fuel filter and O2 sensor

MEAN03GT · Sep 2, 2005

sgarlic said:
Nope, it's not a heavy foot, and my car isn't ****ed up. It's brand new. I have 7000 miles on it. Done nothing but exhaust and shifter.

Got 12mpg off the lot with zero mods, 20 something on the highway. It's called piss-poor tuning by Ford.

And who the HELL buys a Mustang to drive the car like a grandmother? If you're concerned about mileage, don't buy a Mustang.

Oh, i thought you meant you got 12 on everywhere, i get 23-24 on the hwy, but i only get about 14 in the city.

And i dont drive that slow.

Mega-Man · Sep 2, 2005

sgarlic said:
Who the HELL buys a Mustang to drive the car like a Grandma?

LOL That one busted me up. It reminds me of people when they put up adds / for-sale stuff and say, "Has been driven very carefully and never raced." Well no wonder they're selling thier Stang--they haven't had any fun with it.

- Mega

MGSTANG · Sep 2, 2005

12mpg is just ****. I get 17 shifting at the shift points.

jstreet0204 · Sep 2, 2005

sgarlic said:
Nope, it's not a heavy foot, and my car isn't ****ed up. It's brand new. I have 7000 miles on it. Done nothing but exhaust and shifter.

Got 12mpg off the lot with zero mods, 20 something on the highway. It's called piss-poor tuning by Ford.

And who the HELL buys a Mustang to drive the car like a grandmother? If you're concerned about mileage, don't buy a Mustang.

The stock eec should not be getting that low of mileage under normal driving. Just because it is new doesn't mean eveything is working right. I'd have them check all the sensors under warranty, but it's your car, and if you choose to accept that milage out of a new car, more power to ya

sgarlic · Sep 2, 2005

Well, I only put maybe 5 miles a week on it.. the majority of the driving I do is to work and back (1 mile) with the a/c blasting, all city driving. So I'm not surprised I only get 12. I'm sure if I drove normally for a tank it'd be higher. Not worried about it.

Kilgore Trout · Sep 2, 2005

To the thread starter: your car simply needs a tuneup mang

Preventitive Maintenance > Any Mod

Jester73440 · Sep 2, 2005

Kilgore Trout said:
To the thread starter: your car simply needs a tuneup mang

Preventitive Maintenance > Any Mod

Thanks I'm going to do plugs tomorrow as well as fuel filter. Whats a good gap for the 4.6? Also this is :OT: but my friend has a 99 grand marquis and was wondering what his gap should be he can't find any books on it.

Kilgore Trout · Sep 2, 2005

Plugs:
Motorcraft AGSF-32C gapped at .054
Use silicone spray to condition and lube the COP rubber boots to help form a good seal and prevent water in plug wells
MAKE SURE you blow out the plug wells before removing the plugs
USE a very light coat of anti-seize on the plug threads only, keep it off the plug shoulder
Torque plugs to spec and check the torque a few weeks later
read this: http://www.bullittarchive.com/html/modules/articles/article.php?id=83

Fuel Filter:
You will need 5/16th spring lock removal tool
Use Motorcraft replacement filter
read this: http://www.bullittarchive.com/html/modules/articles/article.php?id=83

Also, while you are at it:
Clean MAF: http://www.bullittarchive.com/html/modules/articles/article.php?id=77
Clean or replace IAC
Use SeaFoam in all three ways (this will require an oil change as well)
Check air filter
Reset PCM when you are all done

You car will thank you

Kilgore Trout · Sep 2, 2005

Oh, you have a Thunderbird? Hmm, I think most of what I said will still apply...

Jester73440 · Sep 2, 2005

Kilgore Trout said:
Oh, you have a Thunderbird? Hmm, I think most of what I said will still apply...

Yeah it should be the same. Seafoam yeah i planned to pick some of that up too. reset the pcm you just discount the battery for a hour or something right?

Dark Knight GT · Sep 2, 2005

Kilgore Trout said:
Plugs:
Motorcraft AGSF-32C gapped at .054
Use silicone spray to condition and lube the COP rubber boots to help form a good seal and prevent water in plug wells
MAKE SURE you blow out the plug wells before removing the plugs
USE a very light coat of anti-seize on the plug threads only, keep it off the plug shoulder
Torque plugs to spec and check the torque a few weeks later
read this: http://www.bullittarchive.com/html/modules/articles/article.php?id=83

Fuel Filter:
You will need 5/16th spring lock removal tool
Use Motorcraft replacement filter
read this: http://www.bullittarchive.com/html/modules/articles/article.php?id=83

Also, while you are at it:
Clean MAF: http://www.bullittarchive.com/html/modules/articles/article.php?id=77
Clean or replace IAC
Use SeaFoam in all three ways (this will require an oil change as well)
Check air filter
Reset PCM when you are all done

You car will thank you

In addition to what he said, if your car has more than 60k miles on the current front o2 sensors, it wouldn't hurt to go ahead and replace them, or at least give them a look. Bad o2 sensors can be one of the most common causes for bad gas mileage.

Another thing to do is to make sure you buy gasoline from good places, and not from some "roadside" store that you don't know anything about. I always buy gas from Exxon, BP, and sometimes Shell. Nothing else. I also treat my fuel with Amsoil PI additive. It works well. I get around 17.5-18.0 mpg with combined highway and town driving. More highway driving, the better it is.

You might want to make sure you keep your oil and oil filter changed at regular intervals, as bad/contaminated oil can lead to poor gas mileage and excessive wear.

Jester73440 · Sep 2, 2005

Dark Knight GT said:
In addition to what he said, if your car has more than 60k miles on the current front o2 sensors, it wouldn't hurt to go ahead and replace them, or at least give them a look. Bad o2 sensors can be one of the most common causes for bad gas mileage.

Another thing to do is to make sure you buy gasoline from good places, and not from some "roadside" store that you don't know anything about. I always buy gas from Exxon, BP, and sometimes Shell. Nothing else. I also treat my fuel with Amsoil PI additive. It works well. I get around 17.5-18.0 mpg with combined highway and town driving. More highway driving, the better it is.

You might want to make sure you keep your oil and oil filter changed at regular intervals, as bad/contaminated oil can lead to poor gas mileage and excessive wear.

Changed my oil about 300 miles ago and I only run BP and citgo if I have too.Wouldn't bad o2 sensors give a code? I had the car scanned not to long about and they said the o2 sensors were a little weak but still good and that was less then 4k miles ago. can you change just the front ? I have four right?

Kilgore Trout · Sep 2, 2005

Jester73440 said:
Changed my oil about 300 miles ago

Well then I would wait till your next oil change to use SeaFoam in the crankcase but you can still use it in the gas and the intake. Be sure and lay down a huge smoke cloud on your street to celebrate Labor Day

Horrible gas mileage whats the cause?

Jester73440

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