since I replaced the cruise control servo last weekend my car
(92 olds 88/ 3.8L) has been running quite a bit better. Still it has set a code 13 (oxygen sensor failure) twice. It went from 19.5 mpg to 24.1 mpg and it has still set the code 13. I'm thinking about just changing it and wanted your peoples opinion . The one that is in it now is about two years old. It's a Bosch purchased from autozone. I was wondering if you think that Bosch might make a lower quality part for the discount auto stores than it does for say dealers or other outlets. If thats the case would you think an oxygen sensor from NAPA would be of sufficient quality or would you go with a dealer replacement. AS always all replys are appeciated


PS the scanner shows it reads in the 650- 750 mv range when I have the cruise set on 55. Also this car used to get 26 mpg and I've been told that thats a little low. My sons 93 Bonneville on a trip to Chicago (same engine) used to get 35 mpg till he beat the crap out of it. You know kids think their foot has to bury the trottle from a stop.

 

9 out of 10 Oxygen sensor codes are not caused by the sensor. The code merely means that the sensor is reporting something that doesn't match what it should be. The sensor could be entirely accurate and just reporting another problem like it's designed to do. Your scanner may not be updating quick enough but that sensor should be sweeping nearly the entire range multiple times every second. To test it all you have to do is artifically enrich the engine while watching the reading. A quick squirt of carb cleaner in the intake should spike the reading to .800-.900Mv for at least a few seconds before the computer compensates. If it can do that, the sensor is OK. Sometimes you may have to perform that test during the first 10 minutes of a cold engine to make sure it gets hot fast enough. A manual DVOM is the best way to confirm the reading.

 

for the reply. I know the code is just because the circuit is out of parameter. But being it is so infrequent I thought I might just give it a try. Back to my other question about my mileage. does the mileage I posted sound about right or does it seem low.

 

Well tonight I went through all the grounds on the engine and found out there were two right on the same head. They are mounted with two nuts each with a shield in between the nuts. When I removed the first two nuts and the shield the next two nuts were barely tight at all. So I removed them and sanded the eyelet connectors and wire brushed the studs and reassembled. Now I have my full range on the O2 sensor and it is going into closed loop again. Thanks for all the responses and advice and I'll post later to let every one know if that was a fix.

 

That's some pretty good diagnostic work there, congrats.

 

well I thought I had it but this morning it set a code 44 lean exhaust. And this afternoon when I got off work it stalled once and started right up. Don't know what that was about. At least its not the same code. Everyone needs a little variety every now and then. Well I'll go out in the garage one more night and see if I can find anything else. The O2 is still showing a full range and its still going into closed loop and lockup. When I'm doing hwy speeds it seems to settle in the 650-750 range. But the fuel mixture says 14.7 and it is running well.when I drive through town then it will run through the full range. Guess I'll look under the dash for loose grounds or connecters. I wish I had a computer safe tester to check some of these things out. I did notice that when I have the scanner hooked on my way to work it loses its connection every now and then. ( It's just like I unplugged it and it goes to all the base settings. I'll turn it back on and it reads normally for awhile. It isn't because anything acted up or anything because when I turn it back on it's still in closed loop. I'm wondering if something in the computer might be loose or have a bad connection. Or the wiring to the diagnostic link.) Any suggestions. And I am wondering if they can test the computer out of the car. Or does it have to be in a failed state and they can only tell good or bad.

 

I think that thing just takes a simple single wire sensor. they're cheap enough to just change it and put that question to rest. Just specify a Delco brand. You should be able to buy that aftermarket pretty cheap.

 

it last friday altho it was with a bosch from my local NAPA store. I did it because it was cheap enough and it was an easy repair. It worked for about a day then went whacko. Thats when I searched out the grounds and now it is working ( maybe). Get back to me if you think a Delco would be better.

 

Have you checked the fuel pressure on this car?You start with code 13 open O2 sensor circuit and end up with a lean exhaust code 44.I suggest you look at the computer in the car and see if it has red,white and blue connectors where the wires plug in.Alot of those were junk.I have used aftermarket O2 sensors that would not let the the car go in closed loop but it isn't common.Sometimes the exhaust system doesn't have enough ground for the sensor to operate properly.You can run a extra ground if that is the case.

 

and I 'll drive it tomorrow to see if it resets. It may be a fuel related issue. Thats one thing that I haven't checked yet. Maybe tomorrow evening. Although since I cleaned up the grounds it is going into closed loop. It has its full range when driving through town. It just lacks range when cruising at a steady speed (650-750 mv @50-60 mph) The torque converter locks up just as it should and fuel mixture is at 14.7. I've had the computer out and if I remember right the connectors were green and black. How would you hook up a seperate ground to the O2 sensor. These intermittent problems are just elusive as hell. ( when my daughters cavalier was acting up it took going into complete failure before I finally was able to trace it down to the crank position sensor with some good advice from this forum.) I'll keep pluggin along and asking my questions and eventually it will be fixed.I'm wondering if the loss of communication between the ecm and my scanner might be a clue.

 

But I think I'm going to have to replace the servo with a new unit. Because my mileage drops when I hook it up. Like I said before the servo I replaced it with was a used unit, and it doesn't pass the vacumm test. But it still manages to work( it's probably border line.) As far as hooking up a seperate ground for an O2 sensor . How would I go about that.