Just went over to AutoZone as recommedned by a few of you and they pulled a "P0133" code from their OBD2 reader.

The slip he printed out for me says "slow response (heated oxygen sensor Bank 1).
Am I correct in assuming there are two O2 sensors on my 1998 S70 N/A car?
If so, does this mean it is the front sensor or the one in front of the Cat converter?

Is this a fairly easy job for a neophyte auto repair guy? I have a set of ramps I can pull the car up onto.
Just may need a certain type of socket wrench to break the old one loose.

Thanks!

There are 2 O2 sensors, the p0133 usually points to the front sensor which is before the CAT.

What you also need to look out for is a vacuum leak causing the engine to run rich.

The connector plug can be reached from the top of the engine, between the air cleaner and the turbo - look down. Volvo speed has a demo for this.
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My name is Klaus and I am a V♂lv♂holic

Klaus, this car is a N/A one. Will that make a difference?

Nope, just easier to find the plugs for the O2 sensors.

http://volvospeed.com/volvo_repairs_how_tos/sensor_replacement/oxygen_sensor_o2.html

Make sure you look at all of the vacuum hoses, any cracks must be fixed first.
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My name is Klaus and I am a V♂lv♂holic

Klaus,
When replacing vaccum hoses, are most of them the same diamter hose or are there different diameters?

Not sure if all of the vaccum lines that I need to check are readily visible from the under the bonnet or some hidden ones.

While there are 2/3 different sizes, most are one size. Pay particular attention to the elbow pieces, they connect hard vacuum lines to the manifold and other parts.
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My name is Klaus and I am a V♂lv♂holic

Like this:

http://www.ipdusa.com/products/5321/109425-vacuum-elbow-kit

That will do some of them, not the 90degree connector for the fuel pressure regulator (that is the hard fuel line look alike that comes down infront of the manifold).

Check the elbows before ordering replacements.

Don't forget, you will probably also replace the O2 sensor. Make sure it is plug compatible, you do not want to solder and splice wires which adds more problems.
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My name is Klaus and I am a V♂lv♂holic