98 Subaru Legacy wagon is getting around 17mpg after headgasket job & ECU reset, used to get almost 29mpg

[mightGETaSUBARU]

My 98 Subaru Legacy outback wagon has is getting terrible  mpg right now, today I went through 10 gallons of fuel in  about 172 miles, this included about 165 miles on the highway and the rest was city...

 

I am so confused by this, it all started after I finished the headgasket job and reset the ECU, 

 

WHAT THE HECK IS GOING ON, I CAN NOT AFFORD THIS CRAP

 

 please someone help

 

idle is rough some times (normally after coming to a stop)

 

if I did not know better (because I spent a hour looking for it) I would think there was a fuel leak

 

 

[TechJR]

The first place I would be looking at is your timing, both the belts and ignition... An intake leak is another possibility but you'll usually see more problems than just fuel mileage with that. Does it seem to be lacking power at all?

[El Presidente]

I'm not surprised.

 

I thinking if you keep driving it it will get better. The learning curve of OBD2 is fast, but you'e only given it 7 miles of city driving. Don't be afraid to get heavy on the skinny pedal too, you burn most your fuel accelerating, so give it a chance to learn the best way to do it. Just don't baby it...baby it after teaching it what it can do

 

Josh

[mightGETaSUBARU]

I have drove it maybe another 100 miles or so on the last reset...  it's driving me nuts, seems to pull from 65 to 80 pretty fast, well for a N/A autowagon

[john in KY]

My guess is you overlooked a vacuum line when you reinstalled the heads. Had the same symptoms once when I replaced the sensor for the speedometer. Discovered a small vacuum line connecting what I don't know wasn't connected. 

[mightGETaSUBARU]

there are not too many vac lines to mess with, the car actually had several vac lines disconnected before the head job and it ran better, lol