Ive tried figuring it out myself, but im lost. my hhr was getting easily 26 mpg or more. now im lucky to get 9 thru the insta reading. it randomly lost fuel economy. Has anyone else had this issue? It runs fine. but under just small gas insta reading will say 7 mpg. but at coasting it says 20 to 30 mpg. Any advice would be greatly appreciated.

 

to the forums!

Is the CheckEngineLight (CEL) illuminated?

 

According to your bio you have a 1911 HHR. ???

The instant mileage thing is a useless function. You can see those low numbers under acceleration or see as high as 99 when coasting.
Disregard the instant and go by the Avg. Mileage.

 

I randomly wrote that in its a 2009 hhr. i figured the insta was useless i was using it as a reference point. the car isnt losing fuel as far as leaking and runs pretty normal. the low number is the actual average mpg. it stays around 9mpg. which it randomly started doing. one day its average was in the 20s now it wont get past 10

 

Your 2 posts say different things. One says instant is low, the average mpg is OK.
Now you say it’s the average mpg that is low. So which is correct ?
Have you tried resetting the Avg. MPG in the display ? I reset mine every fill up.
Have you done the “pencil and paper” method when you fill up ? Then you could compare it to the dash reading.

If it really is out of wack, you could try the battery lobotomy and reset the computers. (Disconnect the negative battery cable for 15 minutes then reconnect)

 

“I randomly wrote that it’s a 2009 hhr”

Uh No. Your bio still says 1911 HHR.

 

what im meaning is even the average mpg stays under 10 mpg. There is something going on i would assume with sensors or with vacuums. I posted to see if anyone maybe had the same problem or something close to it. I know the actual fuel economy as of right now is 9 mpg.

 

Battery lobotomy as mentioned. Simple stuff first!
while you’re waiting that 15 minutes, check the air filter and clean the throttle body butterfly.
Do Not move the butterfly plate by hand , you will strip the plastic gear’s inside the throttle body

 

When you say the actual fuel economy is 9mpg, is that calculated by filling the tank, driving for a while, and then refilling the tank to see how much fuel vs distance?

Based on what you said, you used to get 26mpg and you get 9mpg now. I find it hard to believe the car would be using 3 times as much fuel and there would not be any drivability issues? You must notice something different (hesitation, surging, etc)?

Is a CEL illuminated (as RJ asked)?

Steve

 

Me thinks there is a lack of accurate information and missing some facts to accurately assess the problem.

It was my experience that the average mpg from the system was close to but did not always match my mathematics using the mileage driven divided by gallons calc.

With blue and fireman do a battery reset. It's be hard to think it was actually getting 9 mpg (down from normal 26) without and performance or CEL issues.