how to diagnose lazy o2 sensors?

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Kind of related to my slight miss at idle topic, that topic got me thinking about the o2 sensors.
how quick should the sensors switch in an efi vehicle? My saturn seems to be switching values twice per second. Is that good or slow.?
 
how do you know they are switching twice per second? do you have an oscilloscope?
 
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Originally Posted By: Vikas
how do you know they are switching twice per second? do you have an oscilloscope?


I have a scantool and can watch the live data and see the values as they change
 
what type of scantool is it.. that may-be all the faster it can pull data off the bus to refresh.
 
It's an actron and it can go faster I plugged it into my wife's car and it was switching so quick you couldn't keep up with it.
 
Originally Posted By: zzyzzx
How many miles are on these O2 sensors, and if they have been replaced before, what brand are they? Personallt I do not trust O2 sensors past 100K miles.


On my 99 SL2 sensor eventually threw a code when it was lazy at 76,000 miles. When I had replacement motor installed with 80,000 miles on it I just changed it. Denso 02 Sensor at Rock Auto was $35.00. It is not like the $800 the dealership charged to change them on the Lexus.
 
Originally Posted By: zzyzzx
How many miles are on these O2 sensors, and if they have been replaced before, what brand are they? Personallt I do not trust O2 sensors past 100K miles.


123,000 and are original not sure what oem brand is ...
 
I had a 97 saturn throw two codes for lazy o2 sensors.

One was a P0133, one was manufacturer specific and had a slightly different threshold.

The car would bog slightly when I gunned it off idle, could feel it as it was a stick shift and just wasn't smooth.

Have you ever done the intake gasket on this? Spray something flammable at the #1 cyl, down by the PS pump. See if the idle levels off.
 
Originally Posted By: eljefino
I had a 97 saturn throw two codes for lazy o2 sensors.

One was a P0133, one was manufacturer specific and had a slightly different threshold.

The car would bog slightly when I gunned it off idle, could feel it as it was a stick shift and just wasn't smooth.

Have you ever done the intake gasket on this? Spray something flammable at the #1 cyl, down by the PS pump. See if the idle levels off.


Yes , it was done at 110,000 miles. I did recheck that and all vacuum lines though.
 
Originally Posted By: ram_man
It's an actron and it can go faster I plugged it into my wife's car and it was switching so quick you couldn't keep up with it.
See, it is the function of the protocol being used in obtaining the data from ECM. Older protocols are extremely slow and that is why you are only getting couple samples per seconds on the scanner. You can NOT accurately count the number transition in a second because the scanner is only getting couple of measurement points in a second.

I hope that makes it clear.
 
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Originally Posted By: ram_man
123,000 and are original not sure what oem brand is ...


At 123K miles, just replace them with new ones. I use Bosch on every car, except Toyotas where I use Denso.
 
Originally Posted By: Vikas
Originally Posted By: ram_man
It's an actron and it can go faster I plugged it into my wife's car and it was switching so quick you couldn't keep up with it.
See, it is the function of the protocol being used in obtaining the data from ECM. Older protocols are extremely slow and that is why you are only getting couple samples per seconds on the scanner. You can NOT accurately count the number transition in a second because the scanner is only getting couple of measurement points in a second.

I hope that makes it clear.


I don't know how it is on newer cars, but on my mid-80s OBD-1 GM, one of the parameters retrieved over the interface is the number of O2 cross counts.
I believe that it is counted internally by the ECM so that it will be accurate regardless of whether the external interface can keep up with each of the individual voltage swings. I checked a data log from last summer and over an interval I saw about 15 voltage swings, while the cross counts value increased by 40. So I think the cross counts value must be counted internally so that it will be accurate.

This is a much older car than the 2002 Saturn, so I assume the 2002 might have a similar cross-counts feature. Or it might not need it at all - the 2002 should have a much faster datalogging interface than mine, I know they were much faster on cars just a few years newer than mine.

==

When looking at that old log, I found a period of steady hot idle and saw about 1.25 cross counts per second. So it switched slower than ram_man's Saturn. This was with a 2 year old sensor. But since it's a much older car, maybe they aren't comparable. The 2002 Saturn sensors maybe are supposed to switch faster, I have no idea.
 
Unfortunately, the cross count is not one of standard OBD-II PID and thus generic scanner can not access it.
 
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