o2 sensors

anyone able to tell me where these jokers are located and how hard they are to replace?

Very easy to replace. The 4.3l engine uses three. Two pre-cat sensors are in the exhaust pipe ahead of the catalytic convertor, and there's one just downstream of the convertor. Need to get an O2 sensor socket (about $7 at Autozone) and make sure the wiring harness is secured away from the exhaust pipe. NEVER use cleaning solvents of any type on the sensors.

Depends on the year of your truck.

My 96 blazer has 4 o2 sensors one on each side of the bottom of the headers. I think the drivers side was right at the bottom and the passanger was about 8 inches up the pipe. The two others are located before and after the cat, about a foot in front of the cat for the one and about a foot and a half for the last one. Replacing mine was I think the easiest thing I ever did, it took longer to jack up the truck ( aside from waiting in line at 3 different autopart stores ) then it did to replace them. I rented the "special socket" for the job but didn't even use it just used a box end wrench but it is always best to have the right tools in case you need um.

did you notice any difference in power and fuel economy?