I have recently had 2 O2 sensors changed on my 98 Contour, V6, 71000 miles. The Bank 1 Sensor 1 and Bank 2 Sensor 2 were changed last week. I know that my car has 4 02 sensors and I need the other two changed also. The problem is that the other two sensors seem to be the upstream sensors and seem impossible to get to around the engine. Does anyone have a diagram of these two sensors or any techniques that could make this as painless as possible.

The bank 1 sensor 1 is the baddest boy, upstream and right next to the firewall. Since you've had that one changed, the rest are like piece of cake, all you need is a 22mm or 7/8" wrench and some penetration oil.

Upstream sensors in our cars are sensor #1, downstreams are #2.

As I've mentioned several times in the past, go to AutoZone and rent their free O2 sensor toolkit. It comes with a crowsfoot that makes that pesky upper firewall sensor very easy to remove.