Change in mpg after air/fuel ratio sensor change
10-13-15, 12:40 PM
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Change in mpg after air/fuel ratio sensor change
Hi, I am new to this forum. I have a 1999 RX300 with about 185K miles that was given to me about four years ago by my aunt and uncle. When they gave it to me, they told me the check engine light had been on for a while, they'd had it checked by Lexus mechanics, no one could find a problem.
A few weeks ago my mpg dropped suddenly from about 16 mpg to 10 mpg. My mechanic (non-Lexus... closest Lexus dealer is three hour drive) said it was my air/fuel ratio sensors. I had them replaced last week, and they also changed my air filter. I filled my tank for the first time this past Sunday, and two days later I'm almost at a half a tank, approximately 12 mpg. I called my mechanic, as I was expecting an immediate return to 16 mpg, and he said it may take a few tankfuls for the computers to "reset" and adjust to the new sensors. That kind of sounded like a bunch of crap to me. Has anyone else had this experience? Does it truly take a while for your mpg to increase after sensor change? They also suggested I either put in a fuel additive or do a tank of ethanol-free gas.
Any thoughts on this? I had a tune-up back in June. BTW, my CEL is still glowing brightly!
A few weeks ago my mpg dropped suddenly from about 16 mpg to 10 mpg. My mechanic (non-Lexus... closest Lexus dealer is three hour drive) said it was my air/fuel ratio sensors. I had them replaced last week, and they also changed my air filter. I filled my tank for the first time this past Sunday, and two days later I'm almost at a half a tank, approximately 12 mpg. I called my mechanic, as I was expecting an immediate return to 16 mpg, and he said it may take a few tankfuls for the computers to "reset" and adjust to the new sensors. That kind of sounded like a bunch of crap to me. Has anyone else had this experience? Does it truly take a while for your mpg to increase after sensor change? They also suggested I either put in a fuel additive or do a tank of ethanol-free gas.
Any thoughts on this? I had a tune-up back in June. BTW, my CEL is still glowing brightly!
10-13-15, 01:20 PM
#2
the ecu does take a little time to calibrate after installing new a/f sensors but the mpg should not be that drastic.
Check to see if your airbox and air filter is seated correctly, as well as the clamps that secure the airbox to the throttle body. If there is a leak, the ecu can be reading unmetered air and dumping fuel accordingly.
Go get your CEL read for the code, it may shed more light to what is the cause.
Check to see if your airbox and air filter is seated correctly, as well as the clamps that secure the airbox to the throttle body. If there is a leak, the ecu can be reading unmetered air and dumping fuel accordingly.
Go get your CEL read for the code, it may shed more light to what is the cause.
10-13-15, 01:33 PM
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Thanks! I'll check and make sure the filter and clamps are secure.
My mechanic read the codes, and he came up with the air/fuel sensor. It's just that after they fixed it, it didn't clear the light...
My mechanic read the codes, and he came up with the air/fuel sensor. It's just that after they fixed it, it didn't clear the light...
10-13-15, 02:48 PM
#4
You can disconnect/reconnect your positive battery cable to clear the code memory. If the CEL shows up again, then the code needs to be read to determine if the a/f sensor is still the cause.
10-13-15, 10:41 PM
#5
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Hi, I am new to this forum. I have a 1999 RX300 with about 185K miles that was given to me about four years ago by my aunt and uncle. When they gave it to me, they told me the check engine light had been on for a while, they'd had it checked by Lexus mechanics, no one could find a problem.
A few weeks ago my mpg dropped suddenly from about 16 mpg to 10 mpg. My mechanic (non-Lexus... closest Lexus dealer is three hour drive) said it was my air/fuel ratio sensors. I had them replaced last week, and they also changed my air filter. I filled my tank for the first time this past Sunday, and two days later I'm almost at a half a tank, approximately 12 mpg. I called my mechanic, as I was expecting an immediate return to 16 mpg, and he said it may take a few tankfuls for the computers to "reset" and adjust to the new sensors. That kind of sounded like a bunch of crap to me. Has anyone else had this experience? Does it truly take a while for your mpg to increase after sensor change? They also suggested I either put in a fuel additive or do a tank of ethanol-free gas.
Any thoughts on this? I had a tune-up back in June. BTW, my CEL is still glowing brightly!
A few weeks ago my mpg dropped suddenly from about 16 mpg to 10 mpg. My mechanic (non-Lexus... closest Lexus dealer is three hour drive) said it was my air/fuel ratio sensors. I had them replaced last week, and they also changed my air filter. I filled my tank for the first time this past Sunday, and two days later I'm almost at a half a tank, approximately 12 mpg. I called my mechanic, as I was expecting an immediate return to 16 mpg, and he said it may take a few tankfuls for the computers to "reset" and adjust to the new sensors. That kind of sounded like a bunch of crap to me. Has anyone else had this experience? Does it truly take a while for your mpg to increase after sensor change? They also suggested I either put in a fuel additive or do a tank of ethanol-free gas.
Any thoughts on this? I had a tune-up back in June. BTW, my CEL is still glowing brightly!
Please read through the sticky threads.
some where in there you will find ,,, by delaying a fix to emission related problems (cel triggering) you may be loosing more money out of RX exhaust. Here in my county, I would not be able to renew tags with the CEL on.
IMHO only use OEM sensors.
If Lexus dealer is far away, you can always visit Toyota dealerships. I am surprised Lexus showed your Aunt/Uncle the door. They should have insisted and Lexus should have brought experts from the area/nation/Japan. [these experts go around the country solving difficult problems]
Salim
Last edited by salimshah; 10-13-15 at 10:52 PM.
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