Bosch O2 sensors? (and a quick question for anyone that does tuning)
Feb 8, 2007 | 02:57 PM
#1
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Bosch O2 sensors? (and a quick question for anyone that does tuning)
Anyone have problems with the bosche o2 sensors? I've heard their plugs suck, wondering about the O2's
Also, my O2 voltages kind of do this cyclic thing. they will both be around 700mv and then one will drop to zero and come back then the other will do this. rinse and repeat. that's not normal, right?
Also, my O2 voltages kind of do this cyclic thing. they will both be around 700mv and then one will drop to zero and come back then the other will do this. rinse and repeat. that's not normal, right?
Feb 8, 2007 | 03:17 PM
#2
Are you talking about the narrow bands or the LSU widebands? I am guessing narrow band, since you are referencing mV. If this is while in closed loop, O2 sensor oscillation, then that is absolutely normal for the O2 mV to swing rich/lean. Typically with long tubes, since the O2 are further back from the stock location, the ECM has to wait for the O2 to process the signal of an intended rich condition. Since the O2 is further back, it will take a while for the ECM to be able to counter the intended rich condition to an intended lean condition. This is how the ECM maintains the 14.68100 AFR while in closed loop, since the narrow bands are only accurate around 14.5-14.9. Does this help? 
Feb 8, 2007 | 03:21 PM
#3
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George, that helps a lot.
Mine aren't "bouncing around" though. Even at idle or crusie, they litterally take turns going to zero- its like a sine or cosine curve. I have stock manifolds. Its not like the go from 500mv to 800mb its like...
710, 720, 710, 770, 700, 600, 500, 400,300,200,0,100,200,300,400,500,600,700,700
then the next one starts- they never do it at the same time.
Mine aren't "bouncing around" though. Even at idle or crusie, they litterally take turns going to zero- its like a sine or cosine curve. I have stock manifolds. Its not like the go from 500mv to 800mb its like...
710, 720, 710, 770, 700, 600, 500, 400,300,200,0,100,200,300,400,500,600,700,700
then the next one starts- they never do it at the same time.
Feb 8, 2007 | 03:32 PM
#4
Oh, I see. 
They sometimes will not oscillate at the same time, so that may be ok. But with stock manifolds, and while cruising they should oscillate like this (in a span of ~5 seconds):
/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ going from ~100mV to ~900mV.
If they are going like this (in a span of ~5 seconds):
/------------------\________/--------------------\_________________/
Then there might be something wrong with either the O2 heater or the sensor itself, or the fueling. Do you have any trouble codes showing? Sometimes the ECM will store the trouble code for a while, before triggering the SES light ... in hopes that the problem will solve itself or was a fluke. When the ECM sees it again, it will throw the SES light, looking for help.
They sometimes will not oscillate at the same time, so that may be ok. But with stock manifolds, and while cruising they should oscillate like this (in a span of ~5 seconds):/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ going from ~100mV to ~900mV.
If they are going like this (in a span of ~5 seconds):
/------------------\________/--------------------\_________________/
Then there might be something wrong with either the O2 heater or the sensor itself, or the fueling. Do you have any trouble codes showing? Sometimes the ECM will store the trouble code for a while, before triggering the SES light ... in hopes that the problem will solve itself or was a fluke. When the ECM sees it again, it will throw the SES light, looking for help.
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