Posted: 4/27/2013 4:50:26 PM EDT
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I drive a 2006 Toyota Matrix, bought new in Dec 2005. The car is now over seven years old, and has been very reliable. The first and only problem it ever had occurred some months ago--it started stumbling while driving. I took it to the Toyota dealership, where they ran the codes and told me it needed a new fuel/air sensor. They replaced it and I went on my way. The car has about 53K on it now, not high mileage everything considered. The car runs fine, but its fuel mileage seems to have dropped a bit since the sensor was replaced--I used to get about 33 mpg city, now I'm lucky to get 30-31 mpg. Could changing the fuel/air sensor affect the car's fuel mileage? Anything to know?
Thanks! 
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The only thing I can think of that would be a 'fuel/air sensor' would be the upstream O2 sensor, which provides feedback to the computer as to whether its running rich or lean.
Are you calculating the mileage by hand or going off of the computer? If it were me I would start with the basics / fundamentals - fresh air filter, plugs, etc. I suppose in theory its possible to have an O2 sensor thats 'off' compared to the OEM one, but I haven't seen it happen (yet). You'd need a scan tool to verify that, and usually it would set an 'insufficient switching' code if its faulty though. Stumbling when driving doesn't sound to me like its an issue with the O2 sensor, usually that's more of a running rich/lean thing. Stumbling would lead me to believe that its ignition related or fuel related. |
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Quoted:
Did you start using the fed mandated gasahol about that time? No, but it was winter when the car acted up, winter gasoline was in use at the time, which gives poorer mileage by itself. They change the gasoline mix by season here, I waited until the summer mix is in use to know for sure. I try to avoid the gasohol crap. I calculate fuel mileage by hand. I just put a new air filter in. I have not changed plugs. When the stumbling problem started, I got a check engine light at the same time, which prompted me to take it in the next day. The car seems to run fine now, the mileage is just a bit lower than before, 10% or less. |
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Any time I stall out in my 2000 celica it'll run like crap till I reset the ECU by pulling the fuse. I also cleaned my Mass Air Flow sensor at 80K miles and that was a big improvement at the time.
Oh, I also get less gass mileage on my Yoko tires compared to Kumho tires that I miss. ( about 10% and the road noise is getting really annoying) |
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Quoted: Any time I stall out in my 2000 celica it'll run like crap till I reset the ECU by pulling the fuse. I also cleaned my Mass Air Flow sensor at 80K miles and that was a big improvement at the time. Oh, I also get less gass mileage on my Yoko tires compared to Kumho tires that I miss. ( about 10% and the road noise is getting really annoying)  10% change between two similar sets of summer tires? |
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Quoted:
Quoted:
Any time I stall out in my 2000 celica it'll run like crap till I reset the ECU by pulling the fuse. I also cleaned my Mass Air Flow sensor at 80K miles and that was a big improvement at the time. Oh, I also get less gass mileage on my Yoko tires compared to Kumho tires that I miss. ( about 10% and the road noise is getting really annoying)
10% change between two similar sets of summer tires? It's the only thing that's changed. Same plugs, same mobile 1 oil (changed every 3k), same drive to work, same napa gold oil filter. Only thing that is different was the tires because discount tire was out and the guy talked me into them saying how much better they were compared to the Kumhos. I use to get 300 to 310 miles between 1/4 tank fill up now its between 270 and 280 consistently for the past year, and it takes about 10 gallon to fill the tank. Only other thing maybe wheel bearings, but it doesn't sound like a whirling noise and no change in sound on corners. |