Originally Posted by
gointoscott
Our S4's come with 4 O2's the front two go right behind the turbos in the precats - these control air - fuel mixture these are a must for car to run correct and will affect gas milage. if you get codes for these they will say S1B1 (sensor 1 Bank1) S1B2 (Sensor 1 Bank 2)
The rear o2's are more to control emissions and are not necessary for running of car but more for environment. Stock these are located right before main cats after precats. If you get codes for S2b2 or s2b1 these are for rear o2's
Now for your mechanic to say he cant replace the o2's that tells me you might have aftermarket dps and the rear o2 holes are plugged or it doesnt have any and sometimes people will even just lay their rear o2's up by the battery which will throw a code for rear o2's.
If you have just cat back exhaust that shouldnt of affected the o2's at all so something tells me there is more to the story. Have your mechanic explain to you more what he means.
Now the part about gas milage a properly running S4 will see average of 22-23 mpg sometimes more or less depending on circumstances. As everyone is stating.
Who ever said 42 mpg is very hard to believe. If wind at back, and on freeway such as I80 in wyoming heading east which is long and gradual decline I could see as only possibility of getting that good of milage in our cars.
One last thing about milage will depend if you have the 10% ethanol blend in your state - this will decrease your milage a little.
Cheers
Hey, thank you SO much for the detailed response. I now understand the problem so much clearer. I am going to the mechanic this week and going to write down the code that he tells me are showing on the meter.
So from what your saying, the front sensor 1 bank 1, and bank 2 o2 sensors can absolutely be put in since they have nothing to do with the exhaust, right? And the front o2 sensors are the ones that are a Must and the ones that affect performance, and gas mileage? Then i should Deffffffinetely get those fixed because I let my friend drive my car and he said that it is not acting up to its power. He said the o2 sensors not only affect gas mileage, but performance as well.
One last question, if it needs to come to the point where i can get the front ones replaced (since they have nothing to do with the exhaust) and if the only way to get the back ones replaced is to put stock exhaust back on, then is it a big deal to just leave the back ones as it is, and just change the front?
thanks a lot!!!
Reply With Quote
Bookmarks