14 mpg - I need help!

Free2drive! · Post by **Free2drive!** » 23 Sep 2010, 14:08

Hello again,

Started with a full tank, ran 192 miles filled up with 13 gallons.

Drove my weekly commute 38 round trip (6 miles round town and 18 at 50 mph).

Not driving with foot to floor but steadily.

My muffler is being replaced tomorrow, my back box is shot with holes, would this cause such bad gas mileage?
Usually I get 23-25mpg. No codes! Car is 94 turbo auto 140k miles.
Thanks
Matt

Post by **Ozark Lee** » 23 Sep 2010, 16:33

Hmmm,

With no codes it could be anything. Is it possible that you have a fuel leak?

Volvos are very good about posting codes even if they have not yet met the criteria to throw a CEL.

How does the car drive otherwise?

...Lee

Free2drive! · Post by **Free2drive!** » 24 Sep 2010, 08:54

Ok, I got a new muffler fitted from the cat back. Car is much quieter and feels smoother.

It's too soon to tell if my gas mileage improved but I guess a week of commuting will let it show.

Regard
Matt

xjflexer · Post by **xjflexer** » 24 Sep 2010, 12:04

I honestly cannot see a leaky muffler causing such a drastic decrease in fuel mileage. If the car is running fine (as you said, no CEL as you stated) I would look into a possible sticking brake caliper/slide pins.

oh-la-la · Post by **oh-la-la** » 24 Sep 2010, 18:57

Hi
I'm too having the same problem with my 95 T5 wagon. I drove it very gently and easy last hoping to get the best MPG record and the best I got was 14.9 MPG. Last 2 tanks were used under normal daily driving habit ( with some boost) and got 12.4 MPG. The car runs nice, no codes! This is killing me too.

Post by **jblackburn** » 24 Sep 2010, 19:16

My slow decline in gas mileage was eventually traced to a bad O2 sensor. I was getting about 14/20 hwy. I never had any codes, but I had pretty much eliminated everything else. At 170,something miles, it was about time for a new one anyway. The one I pulled out was covered in a white crust, so it had probably needed to be replaced for some time.

Trace down ANYTHING else you can find though, first. Vacuum leaks, clean the MAF sensor, rule out leaking injectors, pre-cat exhaust leaks, a bad fuel pressure regulator, etc.

pablotar · Post by **pablotar** » 25 Sep 2010, 06:18

My mileage improved by at least 7 mpg when I fixed my airbox thermostat.
I'm not sure if your model has that, but it's worth a look.

check out this post:

https://www.matthewsvolvosite.com/forums ... php?t=8830

Free2drive! · Post by **Free2drive!** » 30 Sep 2010, 07:24

Well, still struggling to get 18 mpg even at highway.

New exhaust, from cat back
New plugs from Volvo
New air filter

What else can cause bad gas mileage? It used to be 28 mpg on the highways.

Thanks
Matt

Post by **Pauloil** » 30 Sep 2010, 08:10

after a drive, see if one of the brake rotors is hot.
+1 on the airbox thermo: this alone helped my mpg a lot!
what is tire pressure and batt. voltage?

Post by **jblackburn** » 30 Sep 2010, 08:17

Are you getting black smoke/a rotten egg smell while driving?

Has the front O2 sensor ever been replaced?