Oxygen Sensor ================== According to Arnie Mjelde (Saab Scania of America), the reason for replacing the sensor is that carbon deposits build up over time, reducing its efficiency. He suggests using a torch (2500 Deg. F. is fine) to "clean" the deposits off. Be sure to use antiseize (or equivalent) on the threads or you will never be able to remove it again. I believe that the last sensor I bought (at the full new part retail price) from my local dealer was in fact recycled in this manner. Jonathan Freidin Kendall Square Research Corp. ================== they are usually cheaper from a good foreign parts place (in the Northeast, Foreign Autopart is a good candidate.) Remember to use some sort of anti-seize compound on the threads before installing one. On 79-80 turbos this is a mildly tricky job due to the cramped space; a 22mm deep socket may be of some help. richard welty ================== I went to the SAAB dealer today (Manhattan Beach CA) to get a part that I knew an independent wouldn't have and while I was there I asked about the price on an oxygen sensor for my 83. To my great disbelief the price has gone DOWN from about $90 to $52. Does this mean that the price at an independent parts store will go down also? Anyone price one lately? I went ahead and picked this one up since it was convenient but if someone has gotten one cheaper please let me know. Thanks. Jon King ================== My wife had a 1979 Volve 264 GLE with a bad O2 sensor. The primary symptom that we noticed was a bad hesitation problem (hot or cold). Lots of people tried to fix it (the hesitation, not the O2 sensor) until we finally took it to a shop that knew it was the O2 sensor. They had a cheap and highly effective fix: they disconnected it. No problems ever again (till it was wrecked). - Gil Neiger gil@cc.gatech.edu ================== > Anyone able to tell me how to _measure_ when or if > an O2 sensor is bad, and what the unambiguous symptoms are? You disconnect the wire (not at the sensor end, but the other end) while the engine is running. If it makes a difference to how smoothly your engine runs, the sensor is still effective. Yes, the frequent changing is more so that the car companies can cover their rears - or, even more true, make some money. You don't need to change it anywhere near as frequently as they ask you to. I have all this from a Saab shop. Sharat Israni ================== well, i don't know if his sensor is good or not; but i have encountered mechanics who failed to fix problems while claiming an O2 sensor was good, and when the sensor finally got replaced, the car magically started working correctly. given that you can get 1 wire sensors for less than $40, and 3 wires for less than $100 if you shop smart, and that they're not that hard to replace, i would think that changing them out might be cheaper than paying a mechanic to fumble indefinitely. cheers, richard ================== Most Saabs since 1988 have circuitry that will cause the dash light to come on when the O2 sensor goes bad. The models that have it were described in a service bulletin reprinted NINES a couple of years ago. I don't recall the specific models, but my '88 900S with the 16 valve engine supposedly has this circuitry. Just the same: at the 120K mile service, the engine light had not been on and I told the dealer not to replace the O2 sensor. They called and told me it was bad and they couldn't adjust things properly without replacing it. At least it had dropped $50 in price since the 60K mile service! And the engine did start running much better. With regard to the charcoal canister, that is part of the emissions system, and good citizens take care of the air, right? ================= i can't speak for the carbon canister, but The Oxygen Sensor is Your Friend; take care of it. seriously, there is now a Bosch Universial 1 wire sensor for those cars that take 1 wire sensors for about $30; for those cars that take a 3 wire sensor, there is no Bosch Universal yet, but you can go to your local Ford dealer and have them look up the 3 wire sensors for the 5.0 Liter mustang; there are two different sensors, both of which work; the only difference is the connector -- cut, splice and solder the wires, and go your merry way. all bosch 1 wire sensors are the same except for connectors; ditto for bosch 3 wire sensors. cheers, richard ================== I just had my car in for the 60K, and the mechanic didn't replace them. He told me that I'd know when the O2 sensor went bad, and I didn't feel that several hundred bucks was worth it - it'll go into the 'limp home' mode without it, so I won't be stranded. I don't know if he did the canister, that might be required. A couple of thoughts on the O2 sensor: If you're going on a trip, and are past the replacement interval, it might not be a bad idea if you're a worry-wort to buy one & put it in the trunk. That way, you have a new one, so when you're in, say, East Kearny, Nebraska, you can have any grease monkey put the new one in if needed. Yes, you'll have the money tied up, but you'll need it eventually anyway. I also understand that the 3-wire sensor that SAAB uses is used by most other European makers, and you can buy the VW one for a lot cheaper than SAAB's. Allegedly it's the same Bosch part number, I'd check with Bosch or the part number before trying it, though. I know for a fact that you can get them considerably cheaper than the dealer price, by knowing what to ask for. ================== I haven't because the Saab dealer and an independent Saab shop says it's not necessary but I wonder if this is contributing to my cold start problem. Have you ever had your oxygen sensor replaced? I haven't, and all the mechanics (even the dealer) says mine is still good and not to waste my money, although I'm sure mine is original and it has 125k miles on it. I always wonder if this could be part of the problem. (Probably not though because I can still get 30 mpg highway if I try, and a bad O2 sensor usually means poor gas mileage) But Saab says to change it every 60k. Hmmm... Jason Velasco ================== There is no way to really test the sensor. Although, you could keep driving until you see a marked drop in performance and mileage, which _may_ indicate the oxygen sensor is bad. Saab recommends the replacement of the sensor at 30,000 for non-heated (8valve), and 60,000 for heated (16valve). Some 1988 (900 & 9000 "S" only) and all 1989 and later models do not need this replacement to be carried out automatically, as the LH system monitors the sensor, and produces a fault code when the sensor has failed. ================= Several people on the net have noted that although the OXS service light comes on every 60K miles, it doesn't always need to be replaced then. The thing is, you need a way to test it to know if it really is bad and should be replaced, because a bad sensor will screw up the feedback loop in the FI computer and cause your mixture to be wrong, which can do nasty things such as fry catalytic converters. I'll pass on a neat trick I learned from my cousin, a Mercedes mechanic - Mercedes uses Bosch FI too, so this is applicable. Using a digital voltmeter with reasonably high impedence (20K ohms or so), you can measure the voltage output of your O2 sensor while it's connected to the computer, with the car warm and running of course. Just find the single wire connector coming from the sensor that goes to the computer - not the one that has two wires, that's the preheater on some sensors. Set your meter to a range near 1 volt - the sensor's output falls in the 0-1 volt range. Ground the (-) probe to the head or the battery, and clip the (+) lead to the sensor output. You should be getting a reading in the neighborhood of 0.45 volts, fluctuating a bit up and down. If you get no voltage or a low voltage, your sensor needs replacement. This assumes that your fuel mixture is correct (i.e. nobody played with the mixture adjustment screw on K-jetronic cars) and everything else is in good running order. Anything which changes the oxygen content of the exhaust will change the reading you get, so keep that in mind. -------------------------------------- #6924 4/6/96 Message from Andrey Karachintsev (andrey@ripples.gso.uri.edu) Subject: Oxygen Sensor and Gas Mileage ================== Just wanted to share my recent O2 sensor experience with everybody. I have 900 86 which uses the one-wire sensor. I noticed that over last 6 month my gas mileage has dropped quite a bit. I drive about 300 mi a week and had to put about 13 gal. of gas in the tank to do this. I always thought the O2 sensor was too expensive to be justified economically. But one day I decided to ask...and to my surprise found that you can get one for around $30! They had two options - one with a long wire - $40 and one with a short wire which I ended up getting for $30. It is Bosch part# 11027. It is already treated with the antiseize compound so you don't have to worry about that. It took me about 15min of my time to replace the sensor. The result has surpassed all my expectations - I have to put only 10 gal. a week now, i.e. saving about $5! This means I will get my invested money back in just 1.5 month. After that - pure You also get side benifits like improved idling, etc.... ================== EOF The Saab Network saab@network.mhs.compuserve.com Keith Grider also writes: I used a 1990 ford mustang (5.0L v8) bosch sensor. I read on another site about getting the matching connector from a ford dealer for 10.00 or so and making an extension cord out of the cable from the original Saab sensor. I got the sensor at a local auto parts house for $40.00 and they are always in stock. When I get the connector part number, I will post that back as well. This way, you can replace the sensor with the cheaper ford part the next time and not have to crimp any more wires and have to possibility for shorting, etc. ------------- I needed to replace my front exhaust pipe on my 1989 Saab 900 and could not remove the old 3-wire oxygen sensor (I even placed it in a vice and cranked on it, but no loosing what so ever). I assume no anti-seize compound was used during installation - if you want to ever replace the O2 sensor w/o replacing the exhaust pipe, remember to use anti-seize compound. I read in this page of the Saab Network about substituting the recommended 1989 Saab 900 oxygen sensor (Bosch PN 13028) with the 1990 Ford Mustang 5.0L V8 (Bosch PN 13942), splicing the Saab connectors on it. I referred to my Saab repair manual regarding the oxygen sensor, and it said that the resistance between the heater wires (the two white wires) should be 4 ohms. I tested the Ford O2 sensor I bought and it measured 3.7 ohms (which I believe to be a sufficient match). The dealer quoted me $296.40 for a new Saab O2 sensor and I bought, spliced, and installed a new Ford O2 sensor (which was in stock) for $39.99. Note: soldering did not work well to splice the wiring, which I believe is stainless steel, crimping is more stable. I thoroughly appreciated the accurate information I got on this subject from the posts on The Saab Network web pages. The exhaust system is working well and I anticipate improved gas mileage! This information saved me as much as $260 on this one part alone! Thank you! -Chris Johnson (1989 Saab 900 4cyl. 2.0L 16-valve owner)
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