i have a Ford F-150 4.2L V6 engine with 150000 miles. My problem is that once I start the truck, it feels like normal but once i change gears, it starts trembling and only gets worse when i accelerate. I already changed the fuel filter, but that didn't seem to help. the diagnostic shows that both oxygen sensors are not working, but I just want a second opinion before i buy both sensors, which cost $90 a piece. thank you!

 

I can't tell you what else it might be - What specific codes are being thrown ? And for parts check out rockauto.com.

 

There are 4 O2 sensors...my 4.2 was throwing codes on 3 of them about this time last year. Ended up being a fried MAF, which was screwing with the entire computer.