Volvo: 1990 240 FPR, fuel pressure regulator, roll of quarters

Question
Hey,

I tested the fuel return line today to see if the pressure regulator was working ok, and based on the fact that gas was pouring out, I believe it was.  This brings me to the o2 sensor.  This car was bought used and I don't know if the sensor has ever been replaced.  Could you just tell me where the o2 sensor is located and where it connects in the engine compartment, and how much we could possibly be looking at to get it replaced?  Thanks Jason


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Followup To
Question -
Hey Jason,

The check engine light on my 240 came a a couple days ago.  I ran the fault codes and got a 232 and a 113.  Both these codes have something to do with the  fuel trim being too rich/too lean.  When you get out  of the car after driving, it stinks of gasoline, leading me to believe that the trim is too rich.  The car runs fine, but it idles very slow (almost as is it's going to stall) and stalls intermittently.  I've been looking at a lot of stuff on the internet and I'm starting to think that the fuel pressure regulator might be shot.  I've seen that to test the FPR you simply disconnect the return hose, and if no fuel comes out then you know the regulator is shot.  Just wondering if this sounds right and if you could tell me the ease of doing this repair myself?  Thank a lot!
Answer -
Based on the gas smell, I'm going to agree that you're probably running rich.  I also agree that the FPR is a good test, and could be the culprit.  I would also check your O2 sensor; when they go bad it can cause the ECR to run a rich mixture too.  Finally, check the air mass meter, which can fail and cause an overly rich run too.  Good luck!

Answer
The O2 sensor is screwed directly into the exhaust manifold, pointing toward the firewall.  It's about the size of a roll of quarters, and usually looks silver.  On your 1990, it should be a dual wire, pre-heated unit, so expect to see wires coming out the back.  You need a special long socket to get around it and unscrew it, but you can rent those from your local Kragen, etc.  The O2, as stated in the manual, needs to be replaced at least every 50K (on my older one it says every 30K), but newer ones last longer.  If it is the original, then a replacement is definetly in order, even if it isn't the cause of your problem, because they can affect gas mileage, emissions, and general performance when they get old.  My O2 sensor cost about $35, but I have an older style single wire that I've heard is less expensive then for newer models.  I would be prepared to pay more then that, but I'm not quite sure how much.  A quick call to Pepboys will answer that question.  Once you get the socket and replacement sensor, the job is very easy to do on your own.  Just make sure the engine is COMPLETELY cool, and also, when screwing in the new sensor, be gentle and don't over tighten!  Good luck!