Just filled the tank, and after calculations, It's about 16.5 mpg in the city. Not sure if that's still considered "low", but its definitely a lot better than before. I'll be replacing all the air filters which will probably help a little, as well.

 

Certainly an improvement. I'd guess city only this time of year should be a little better, probably in the low 20s.

 

Go back to checking your fuel trims like before. Let us know what they look like.

If you didn't replace that cracked rubber piece, use some electrical tape to seal it up then see what happens to your fuel trims.

 

Changing the airfilter on a car with modern fuel injection will not in any way improve fuel economy.

 

Mr Shipo..Hate to disagree with you BUT :::
If the air filter is dirty ( plugged ) it will certainly affect fuel economy

If your air filter gets too dirty or clogged, your engine won't be able to suck enough air into the combustion chambers. The engine will then run rich (i.e., too much gas and not enough air). ... If you really neglect the air filter for a long time, your car may stop running altogether.

 

Nope, sorry, doesn't work that way, clearly you do not understand how modern fuel injected engines operate. The short explanation is modern engines weigh the intake charge downstream of the throttle body and then inject the correct amount of fuel into whatever air is there; it matters not whether the air is restricted by a closed throttle plate, a clogged air filter, or even high altitude, the air to fuel mixture remains correct regardless.

For the long answer read this:

• http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

 

@PAhonda

I checked the fuel trims earlier, and they're wildly different than before my initial reading. They ran about the same for both idle and 2000 RPM. There were small "burps" but not super drastic.

Short fuel trim held steady at -6.3. Quickly jumped to ~-0.8 then back again when I let my foot off the gas.
Long fuel trim held steady at -7.8 but quickly jumped to -3.8 then back again when I let my foot off the gas.

 

This thread is getting long with some items that aren't clear with the current state of your car.

1. Are you getting any codes after the repairs?
2. What repairs have been completed since you had the very low fuel trim?3. From your last post, did you get a -15 (-6.3 + -7.8) total fuel trim at idle, then a - 4.6 (-0.8 + -3.8) at 2000 rpm?

 

I apologize for the lack of information!

• No CEL's since the repairs.
• Both O2 sensors were replaced. The cracked transmission seal were replaced, as the crack was causing trans fluid to spray all over the upstream O2 sensor. The cracked rubber boot which was in the picture earlier in the thread was replaced at the time, as well.
  • After the CEL repair, the car got an alignment, balance, and rotation (this Monday to be precise). This was after the 16.5 reading, but that probably doesn't play a big role.
  • Air filters have not been changed as of yet, but will be next week.
• Fuel trim results:
  • At idle: -7.1 (ST was -0.8, LT was -6.3)
  • At 2000 RPM -13.3 (ST was -7.0 LT was -6.3.)

I am recalculating MPG currently and will report back.

 

After running the tank empty and filling again, I'm getting a little under 19 city mpg (18.74 to be exact). Heck of a lot better!

Thanks all for the help!