Help!!!!97 Cobra Only Getting 14 Mpg!!!

EPIK · Dec 16, 2005

I have had my 97 cobra for about a month now, and its getting very crappy gas mileage. The car has only 89,000 miles on it, and so far I changed the plugs, fuel filter, and all the fluids. The only problem I have noticed is that it idles a little rough. Not so rough that it feels like its gonna die, but it just doesnt idle very smooth compared to the 96 gt I used to own. as far as I know the car is completely stock besides a drop in K&N. I would assume it doesnt have aftermarket gears because it tachs at 2400 at 80 mph, and I doubt it has non stock cams in it. The last time I filled up I had only put 177 miles on it and it took 12 1/2 gallons. Doing the math this equals 14.3 mpg. I know its a cobra, and I get on it every once in a while, but i thought my gas mileage would be better than this. Could my rough idle be the root of this? What kinda gas mileage are these things supposed to get? Any advice would be appreciated.

trailblazr81 · Dec 16, 2005

KEEP YER FOOT OUT OF IT!!!

Seriously, do you do all city driving? If so I believe the mileage. But you said it idles rough so I'll suggest cleaning the injectors.

Oh yer supposed to get 18/26. http://www.fueleconomy.gov

EPIK · Dec 16, 2005

I do about 50/50 city & highway driving. I guess this tank I will not get on it at all, but its hard to resist. Especially with all these STI's and LS1's roaming the streets lol. So u think my injectors might be causing the idle problem?

mustanggt3685 · Dec 16, 2005

HAHA 18 MPG city with premium (according to the site), that is a touch off.

trailblazr81 · Dec 16, 2005

dirty injectors can cause bad mileage, rough idle, and performance issues. I heard the Feds. are planning to do something about the whole estimated fuel mileage ratings on new cars. Since nearly every car is way off what it says its supposed to get on the window sticker. Before I moded my GT I was getting about 22 or 23 MPG.

EPIK · Dec 16, 2005

I have never cleaned injectors b4. How do I do it?

trailblazr81 · Dec 16, 2005

Best is to have a shop take 'em out and do it using some sort of ultra sonic method. Some oil change garages clean 'em on the car by forcing a cleaner into the fuel rail. You can read up on the different methods here http://www.witchhunter.com/methods1.htm

EPIK · Dec 16, 2005

Which method would u recommend? I already used the kind u put in your gas tank with no success.

blackfang · Dec 16, 2005

Thats because the crap like STP you dump in the gas is diluted before it hits the fuel injectors and you have a better chance of piss cleaning the injectors better. I suggest you go to autozone and get 2 cans of seafoam(12 bucks total) and put one can in the tank, and half the other can in your intake via pcv(a black l shaped plastic vale/hose on the drivers side valve cover that goes into the intake).

Start the car up, undo the pcv and pour the can slowly into the pcv(actually it will suck it in). Be slow as the car is idling funny due to loss of vacuum and you can stall it. Once you done half the can, close the pcv and rev and hold the car to 3k until the white smoke is gone.

This will clean your filter, injectors and IMRC's much better than that fuel treatment crap you dump in the tank.

EPIK · Dec 16, 2005

I have heard of this Seafoam stuff, but was kinda scared to use it because someone on here said their car was smoking for like a month.U dont think i should just have a shop remove the injectors and clean them?

EPIK · Dec 16, 2005

Also I already removed the valve covers because I had to replace the spark plug seals, and I didnt see any sludge or buildup in the heads.

trailblazr81 · Dec 16, 2005

SEAFOAM!!! It only smokes till its all been burned out. Shouldnt be too long, you should rev ita while then drive around a bit and it will clear up.

tomustang · Dec 16, 2005

EPIKGT said:
I have heard of this Seafoam stuff, but was kinda scared to use it because someone on here said their car was smoking for like a month.U dont think i should just have a shop remove the injectors and clean them?

that happens on very high mileage cars that have carbon buildup holding the engine together, where the carbon is sealing a leak somewhere

bdcardinal · Dec 16, 2005

also you might want to clean your IMRC's. there was a writeup, but the link i had is down. you take your intake off and take the plates out and clean them with carb or brake cleaner. that helps idle and gas mileage a ton.

DBMSTNG · Dec 16, 2005

my neighbor used to have a 99 Cobra. he would complain about his gas mileage and swear up and down he wasn't racing around. so one day i was riding with him and noticed he cruises at 2500rpm!!!

driving has alot to do with it. i could get 24mpg out of my GT with a 50/50 city/highway and i have a heavy ass automatic.

gargol139 · Dec 17, 2005

Don't be scared of the seafoam, it'll make your car feel like a million bucks.

1LowGT · Dec 17, 2005

I too was weary of seafoam but used it and it felt like i added 15 hp i use lucas in the tank though,it always works wonders,get the big bottle of lucas and dump half of it in the tank.

RandyStinchcomb · Dec 17, 2005

doubt if cleaning the injectors will help, Ford has used deposit-resistance injectors since 1991 and little if any deposit will form at 90k. to me it sounds more like the O2's might be going south and maybe in northern Calf, like here in the East they put different additives in the fuel for winter and this has an effect on miliage, you can except @10% loss wth winter blends of fuel.

stangGT97 · Dec 17, 2005

RandyStinchcomb said:
doubt if cleaning the injectors will help, Ford has used deposit-resistance injectors since 1991 and little if any deposit will form at 90k. to me it sounds more like the O2's might be going south and maybe in northern Calf, like here in the East they put different additives in the fuel for winter and this has an effect on miliage, you can except @10% loss wth winter blends of fuel.

I didnt know they changed the fuel blends in the winter, weird.. could you explain that a bit?

Superhereaux · Dec 17, 2005

i'm surprised no one's said "clean the maf" yet:SNSign:

also try to get an average mpg. in other words fill up around 5 times and then figure out your mpg. keep your reciept and write the current mileage down each time

Help!!!!97 Cobra Only Getting 14 Mpg!!!

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