'91 240 Oxygen Sensor Type and Location?
 

Hey guys, I have a '91 240 SE in rough shape and I believe the problems I'm having with rough idle and random stalling are coming from one of a few sensors.

My first attempt at fixing it is going to be replacing the oxygen sensor. Can someone point out the location, and clear up what type of sensor is needed?

I'm looking to get a cheap replacement however even "OEM" parts are listed as universal. Some say 2 wire, 3 wire, 4 wire, and others specify heated and non-heated.

How in the world do I determine which of these types of sensors plus how many wires will be completely compatible and trouble free? Thanks.

First off, is there a check engine light? if there is then check the codes. even if the light isn't on still check. http://www.troublecodes.net/Volvo/

Is that a turbo model? I think it is???

I think it is in the downpipe, about 4 inches away from the turbo. if not then it will be in the exhast manifold (look under the car to see these areas of the car.

I believe the 91 will be the bosch 3wire sensor. someone confirm this?

Wait for the experts to get on...

Actually it is not the turbo model, its the standard 4 cyl. so I guess its not the SE.

Engine code is 232 which is too lean or too rich fuel.

would the oxy sensor be a heated or non-heated model? Whats the difference?

Its heated, with 3 wires. Early models had it mounted in the exhaust downpipe, Later models had it down by the catalytic converter. It's output connects to a thick green wire on the firewall, covered with a rubber boot.

The way to check it is to measure the green wire with everything connected during idle, it should vary in voltage quickly between .2 and .8 VDC.

I would also look for any split vacuum lines.