Hi.
My 96 I30 has a bad gas mileages like 15 miles/gal.(premium). It was 20~21 mlies/gal. in the city after all of the O2 sensors were replaced about 3 months ago. So I guess the sensors is something wrong because the car has been showed to the same gas mileage before the sensors were replaced.
The two front sensors were from ebay by the bulk type which doesn't have terminal plug. It should be connected with old wire.
Are the sensors possible to be broken without any CEL?
Thanks.

 

no i dont think so if anything goes wrong with especially the front ones, u get the cel..

 

Did you reset you ECU?

 

Sure I did serveral times...

 

It would have a CEL if anything was wrong with them

 

tire pressure?
knock sensor?
fuel filter?
spark plugs?

are you throwing any codes at all?

 

Pressure is OK.
Spark plugs are the new ones.
Knock sensor was replaced 3 month ago.

I don't have any CEL so far.

Thanks