2007 Honda Odyssey EX-L with 140,000 miles.
Having trouble determining cause of gas mileage drop. Mpg decreased from average of 21 mpg to about 12 mpg over a few weeks. I have replaced both air/fuel ratio sensors (Bank 1, Sensor 1 and Bank 2, Sensor 1), Fuel injectors, Ignition coils, Spark plugs, and PCV valve. Checked tire pressure and alignment is slightly off, but not significant. Nothing I have done has affected the mileage.
Van does get much better mileage on the highway.
@danyoung
Did you clean the throttle body......
Can you look at live data with your scanner? And did you check pressure at O2 port when you replaced them (cat back pressure?)? I'd check that next.
@hillbilly
I can check live data on a scanner (I have the CreaderVII+). I did not check the pressure at the O2 port. I will have to research how to do that next. Any guidelines on what it should be? Thank you.
Yes, the cat, as I recall, should have less than 1/2 psi difference at idle....can vary of course depending on cat, car, etc. You want to take a pressure reading on the upstream and downstream port...ideally they should be the same (low). I don't think this is the problem but wanted to know if you checked it as when O2 sensor is out is an opportune time to test (I wouldn't worry with testing now). Watch your live data fuel and air (ltft, stft, maf, temp, tpi, map and all O2's. Waveforms ideally).
Does the van seem to shudder at stoplights? If your bad gas mileage is mainly in the city, I'm wondering if there could be a problem with the torque converter or the transmission. Might want to check your trans fluid, see if it looks burned.
Did your driving habits change recently? Everyone hasn't been driving much due to current pandemic.
Also did you use ALL OEM parts? These vans do not like aftermarket parts. Where did you buy the parts? Knock off parts are all over the internet.
