gas gauge problem?

[01Roush]

I'm new to my CSVT, only had it a week. Is it normal for these vehicles to have the fuel gauge indicate that there is very little gas left and then after it sits a while, have almost a 1/4 tank? It seems that whenever I get down to about a 1/4 tank of gas, I will be driving and all of a sudden the low-fuel light comes on and the fuel gauge reads almost empty . . . and then the gauge gradually goes all the way back up to about 1/4 tank. Should I be concerned, or just always keep more than a 1/4 tank of gas in the car and ignore this?

I also popped up a 1311 code and it seems that the general concensus on this forum is that I need to replace the upper O2 sensor that sucks to replace. Is this correct, and how long can I wait until something bad happens? The car seems to still run perfectly.

 

[striker2]

there is no P1311. do you mean P1131? if so then you do need to replace the bank1 upper O2 sensor. the computer thinks the engine is running lean on that bank so it will try to add more fuel. aside from lowering your gas mileage it can do other things (although its better to be running to the rich side than lean)

 

[01Roush]

any advice on the gas gauge fluctuations? and yes, the code was 1131.