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Hi i have a Honda civic 2007 at and its mileage is really low ... Somewhere around 7 to 8 kmpl in city . how to deal with it... And at times in neutral my rpms keep shuffling up and down . Need help .

 
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CEL on?

 
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yes there is air fuel ratio error on the scanner ... And the cel is on

 
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well that could certainly cause fuel mileage problems. sensor probably needs to be replaced, make sure its plugged in first. and buy either a denso or ntk

 
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Is it the upper sensor or the lower sensor ... There are 2 sensors .. The upper i mean near my engines face .. And lower below near the suspension

 
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upper

 
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Thanks alot .. How much does it effect the mileage .

 
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It can reduce it by 20% or more.

 
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Are you sure it is the upper one that goes faulty always .

 
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Either one can go bad depends on what the CEL is and what kinda problems you are having. The upper one determines A/F ratio while the lower one checks to make sure catalytic converters is working properly.

 
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It is an air fuel ratio error so hence it might be the upper one .Thanks for helping .

 
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Yes the upper would be the problem and you are experiencing bad gas mileage which is another symptom of it being bad.

 
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Ordered an upper one .. Today ..it is P0135 code the error

 
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P0135 even after air fuel ratio sensor change .

 
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You did a ECU reset?

Denso or NTK sensor?

 
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Its a denso .. The mechanic did clear the code after installing it through the sensor but it reappears . how to reset the ecu system ?

 
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I had another issue today in which the ac fan motor was running slow and that lead the coolant to come out twice from reserve coolant box so i changed it. Would it again happen or was it just because of the ac fan running really slow .

 
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My car overheats even after getting the car cooling system checked completely .

 
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Head could be warped depending how bad it overheated.

 
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I just got a head gasket changed a few days ago .But its even bad after the job done . however the temp Meter shows no signs of overheating even after the ac fan motor replacement but i feel the heat when i open the bonnet