Someone please help me out, I ve been getting very low mpg, no codes, no fuel smells, car runs and drives all too well. No sputtering, no hard starts jus burns lots of gas. Changed o2 snsors and air filter. Wats wrong!?
10 MPG! 95 4.9 Deville Concours
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Re: 10 MPG! Please help! 95 4.9 deville concourse
:welcome:
Where and how are you driving? If you are doing all city driving and are the guy who has to be the first off of every light and are into the throttle to get it up to speed as quickly as possible, 10 MPG might not be out of line. If that's not the case, check for a leaky FPR. That could easily lower your mileage.
:welcome:
Where and how are you driving? If you are doing all city driving and are the guy who has to be the first off of every light and are into the throttle to get it up to speed as quickly as possible, 10 MPG might not be out of line. If that's not the case, check for a leaky FPR. That could easily lower your mileage.
Re: 10 MPG! Please help! 95 4.9 deville concourse
Thanks, I'm in Nashville TN. I drive normal stop n go and some interstate. I didn't have this problem til about june or august?, not sure. But when I bought car in march I was getting average mileage like 14- 18 . I started using Octane booster too often on 87 gas when I knew I should have used 93.
Thanks, I'm in Nashville TN. I drive normal stop n go and some interstate. I didn't have this problem til about june or august?, not sure. But when I bought car in march I was getting average mileage like 14- 18 . I started using Octane booster too often on 87 gas when I knew I should have used 93.
1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
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Re: 10 MPG! Please help! 95 4.9 deville concourse
is it a 4.9 or concours? They aren't the same thing.
Have you changed spark plugs yet? DId your driving habbits change? 10mpg can be normal depending on the time of year if it's winter over spring or all city driving like Ranger said.
is it a 4.9 or concours? They aren't the same thing.
Have you changed spark plugs yet? DId your driving habbits change? 10mpg can be normal depending on the time of year if it's winter over spring or all city driving like Ranger said.
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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22,634 Posts
Re: 10 MPG! Please help! 95 4.9 deville concourse
FIRST thing is to find out what car/engine you have
a '95 Deville has the 4.9 motor - the '95 Concours has the Northstar motor -
what do you have -
next question - HOW DID YOU LOOK FOR CODES -
did you use the method as outlined here -
http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-
1985/138257-how-pull-codes-dtcs.html
if this is NOT the method you used - try it and post the results -
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FIRST thing is to find out what car/engine you have
a '95 Deville has the 4.9 motor - the '95 Concours has the Northstar motor -
what do you have -
next question - HOW DID YOU LOOK FOR CODES -
did you use the method as outlined here -
http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-
1985/138257-how-pull-codes-dtcs.html
if this is NOT the method you used - try it and post the results -
Re: 10 MPG! Please help! 95 4.9 deville concourse
well we have the craziest weather its like 35 deg.right now. I checked the fpr, but no gas was present at the vacume line. I rodded out the two egr tubes and mpg decreased more. The car runs so smooth and acclerates like nothing is out of wack that's the only reason I never checked the plugs. It just sucks gas like crazy now. I stopped driving it as much for that very reason. I pulled codes by using the "Off and Warmer" buttons. And I have a 95 deville with the 4.9 engine. Its that purple looking color and it used to have extra skirts on the back.
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Could the fpr be bad and still allow more gas to be sucked in and burned without leaking from the line? Or egr? I have noticed that it wants to idle a little bit higher than usual, sometimes the check engine light will come on mostly around 60 or 70, but I still have no change in performance.
well we have the craziest weather its like 35 deg.right now. I checked the fpr, but no gas was present at the vacume line. I rodded out the two egr tubes and mpg decreased more. The car runs so smooth and acclerates like nothing is out of wack that's the only reason I never checked the plugs. It just sucks gas like crazy now. I stopped driving it as much for that very reason. I pulled codes by using the "Off and Warmer" buttons. And I have a 95 deville with the 4.9 engine. Its that purple looking color and it used to have extra skirts on the back.
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Could the fpr be bad and still allow more gas to be sucked in and burned without leaking from the line? Or egr? I have noticed that it wants to idle a little bit higher than usual, sometimes the check engine light will come on mostly around 60 or 70, but I still have no change in performance.
1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
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6,833 Posts
Re: 10 MPG! Please help! 95 4.9 deville concourse
If the check engine light comes on there should be a trouble code or at least a history code for it.
I think lately mine's been getting around 12mpg. I usually don't pay attention. I did see it was -15 out today when I drove to work so that goes far in explaining any bad gas mileage I get.
If the check engine light comes on there should be a trouble code or at least a history code for it.
I think lately mine's been getting around 12mpg. I usually don't pay attention. I did see it was -15 out today when I drove to work so that goes far in explaining any bad gas mileage I get.
Re: 10 MPG! Please help! 95 4.9 deville concourse
If mine would at least get 12.5 i'd be happy, . I'd change the plugs and deal with it. But 10 is jus too low . I might as well put a 455 in my cutlass and drive it daily if ill setle with 10 mpg. But I did have some history codes, I'll check in the morning and post. Thanks to all.
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And by the way, it actually has dropped all the way to 8 mpg, i just reset the trip,average,and instant about 3 weeks ago got on the interstate and let it average out to 18mpg, not even a good 15 min of stop n go street driving it went to around 11.4. Parked for the night, went bout 1/2 a mile to the store and it dropped to 10.4 and has been that way ever since.
If mine would at least get 12.5 i'd be happy, . I'd change the plugs and deal with it. But 10 is jus too low . I might as well put a 455 in my cutlass and drive it daily if ill setle with 10 mpg. But I did have some history codes, I'll check in the morning and post. Thanks to all.
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And by the way, it actually has dropped all the way to 8 mpg, i just reset the trip,average,and instant about 3 weeks ago got on the interstate and let it average out to 18mpg, not even a good 15 min of stop n go street driving it went to around 11.4. Parked for the night, went bout 1/2 a mile to the store and it dropped to 10.4 and has been that way ever since.
Re: 10 MPG! Please help! 95 4.9 deville concourse
P.S.
You're looking for fuel leaking from the nipple, not the vacuum line when you disconnect it. In the above test you may see fuel in the vacuum line.
Rare, but it is possible. Add vacuum (not engine vacuum) to the FPR either with a hand held vacuum pump or by sucking on a length of vacuum hose.
P.S.
You're looking for fuel leaking from the nipple, not the vacuum line when you disconnect it. In the above test you may see fuel in the vacuum line.
Re: 10 MPG! Please help! 95 4.9 deville concourse
I would think if it's running rich enough to cause that low a mileage, you would smell it.
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One more stupid question: Are you actually measuring 10 mpg? As in, record the number of miles you drive on a tank of gas? Or are you going only by what the DIC tells you?
I'm still a bit confused. Only the Concours (Northstar motor) had the extra skirts.
His numbers don't apply. His is a heavier, RWD car with a bigger motor. My '95 averages 18-19 mpg with normal driving. Highway only runs anywhere from 22-26 mpg.
I would think if it's running rich enough to cause that low a mileage, you would smell it.
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One more stupid question: Are you actually measuring 10 mpg? As in, record the number of miles you drive on a tank of gas? Or are you going only by what the DIC tells you?
Re: 10 MPG! Please help! 95 4.9 deville concourse
Not so long ago my car used to not take into account about 3 galons - after half tank had been used; mileage was also low. It later started giving me codes for the EGR on the highway. I cleaned the tubes and the EGR valve many times, but it was the same until I replaced the valve. After the EGR valve replacement my computer started accounting for every bit of fuel used, my mileage went up, and my calculated mileage and DIC mileage agree.
When the AVG mpg is reset it gets pretty sensitive for awhile (it will change the numbers almost as fast as your instantaneous mpg). Get into the habit of resetting the gal. used and Avg mpg just when you fill up, also reset your trip odometer and leave it like that until you have to fuel up again. That way you are really going to let the computer average your mileage. When you fill up calculate your mileage both ways - miles on odo divided by gal. used, and miles on odo divided by the amount of fuel you purchased to fill it up. Compare both numbers and then look at what the computer averages; the numbers should be pretty close.
Not so long ago my car used to not take into account about 3 galons - after half tank had been used; mileage was also low. It later started giving me codes for the EGR on the highway. I cleaned the tubes and the EGR valve many times, but it was the same until I replaced the valve. After the EGR valve replacement my computer started accounting for every bit of fuel used, my mileage went up, and my calculated mileage and DIC mileage agree.
Re: 10 MPG! Please help! 95 4.9 deville concourse
Thanks for the info. I probably will replace egr and fpr at the same time . Just money is low rihgt now. The first 95 deville I had was regular caddy not concourse, and it was burning about 14 - 18 all city driving with 114*** miles on it. This one has 241*** miles on it and drives almost better than my first one. Just started sucking gas a lot after I used too much octane boost, cheap ones at that . Maybe my catalyc converter is fairly new and covering up the smell of to much gas being burned. if this car was for sale , anyone who likes caddys would buy it and would think this car is perfect only if they did not pay attention to how much fuel is being burned and how low the average mpg was. I feel like I'm driving a H2 Hummer.
Thanks for the info. I probably will replace egr and fpr at the same time . Just money is low rihgt now. The first 95 deville I had was regular caddy not concourse, and it was burning about 14 - 18 all city driving with 114*** miles on it. This one has 241*** miles on it and drives almost better than my first one. Just started sucking gas a lot after I used too much octane boost, cheap ones at that . Maybe my catalyc converter is fairly new and covering up the smell of to much gas being burned. if this car was for sale , anyone who likes caddys would buy it and would think this car is perfect only if they did not pay attention to how much fuel is being burned and how low the average mpg was. I feel like I'm driving a H2 Hummer.
1991 Cadillac Brougham D'Elegance 5.7 Litre, 1994 DeVille
Joined
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6,833 Posts
Re: 10 MPG! Please help! 95 4.9 deville concourse
That's 12 mpg from a 94 DeVille so it does apply. Forum won't let me change my heading to include that car. I wouldn't have bothered saying mileage for a brougham since it's compltely different.
Re: 10 MPG! Please help! 95 4.9 deville concourse
Ok its showing PO/PD. 30,39,and 52 all history and TO83 current . What do these mean?
Ok its showing PO/PD. 30,39,and 52 all history and TO83 current . What do these mean?
Re: 10 MPG! Please help! 95 4.9 deville concourse
The Sticky at the top on pulling codes includes a link to the definitions.
You have issues with the ISC and Torque converter. Seperate problems. Both contribute to poor mpg.
Replacing the ISC is fairly simple. I would start there. The TCC is another matter.
I wonder why you can't change your profile :hmm:
The Sticky at the top on pulling codes includes a link to the definitions.
You have issues with the ISC and Torque converter. Seperate problems. Both contribute to poor mpg.
Replacing the ISC is fairly simple. I would start there. The TCC is another matter.
Sorry about the confusion. That is quite low for a 4.9!
I wonder why you can't change your profile :hmm:
Re: 10 MPG! Please help! 95 4.9 deville concourse
Are you calculating fuel mileage by the information system or the old fashioned way? If it is really burning that much fuel with no codes it must be FPR or leaky injectors. That is still a lot of miles for any engine in my book. Somebody should verify that it has good vacuum. Rich running vehicles usually run pretty good though. O2 sensor and MAP sensor have the biggest influence on mileage. I wouldn't replace either one unless I got a code for it.
Are you calculating fuel mileage by the information system or the old fashioned way? If it is really burning that much fuel with no codes it must be FPR or leaky injectors. That is still a lot of miles for any engine in my book. Somebody should verify that it has good vacuum. Rich running vehicles usually run pretty good though. O2 sensor and MAP sensor have the biggest influence on mileage. I wouldn't replace either one unless I got a code for it.
Re: 10 MPG! Please help! 95 4.9 deville concourse
I have no codes showing now, and car still runs good. MPG is still sit ting around 10.2 - 11
.1, no matter what now,driving hard or granny style. Will a bad fuel filter cause the engine to use more gas?
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Maybe the question is, what causes a car to burn more gas or lose gas mileage,but also has no or hard to see symptoms?
I have no codes showing now, and car still runs good. MPG is still sit ting around 10.2 - 11
.1, no matter what now,driving hard or granny style. Will a bad fuel filter cause the engine to use more gas?
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Maybe the question is, what causes a car to burn more gas or lose gas mileage,but also has no or hard to see symptoms?
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