i have a 1991 f150 with a 302 ...iv puttin headers on it but when i reinstalled the o2 sensor there was a bung in the last cylinder pipe on the passenger side so i drilled a hole in the pipe and put it in there... now people have been saying i should have put it in the collector for better reading..should i buy another o2 sensor and weld a bung to the collector and just keep the old one disconnect in the header so i dont have a leak?? could this cause a bad drop in gas mileage ....iv gotten better in my old 351

 

Yes it could cause a drop in gas mileage. How are you calculating your mileage? Is your odometer accurate? If you put larger tires on it, did you calibrate the speedometer?

 

I havent checked my mileage..its just I went though $45 in gas for the past two days ....iv only got 31s on it.

 

You need to calculate your gas mileage if you want meaningful help. Otherwise you are just chasing ghosts.

 

is it even worth putting in another o2 sensor ??? ill have to fill up when i get money and test my mileage

 

02 censor isn't cheep. see how many miles you get out of youre next tank and take it from there. i get 11.5 average with only exaust

 

My mileage is around 9-12 based on how I drive it 95 250 4x4 with a 460 v8. I'm just curious what "bad" is?

 

If the O2 sensor is bad a code should be showing, get the codes before you start slapping new parts (just so you don't end up replacing parts in good working order).