Oily oxygen sensor?

[Ox1]

On my wifes 96 Burban with 206K on it, we are having trouble keeping oxygen sensors in it these days. Once it goes "bad" it throws up the error code and goes from 16 - 10 mpg! My mech says that he thinks it might be from getting an oil film on the sensor. It only uses prolly a qrt per change or so. Mostly hwy miles running parts all over (40K/yr). Not a grocery getter, the exhaust gets warmed up. Also just replaced the cat on the same side I think. (I think it was the same side as the sensor that is going out, but I may just be assuming that? I didn't do it.)

 

Don't tell me I need to build a new motor over a qrt of oil? That is crazy! What gives?

 

I am a newbie here, but I don't think I was going to find this on the newbie board. LOL! I am also sorry if this is a worn out topic, but I highly doubt it. And I have no idea what "key word" to use for such a topic. ?? If it is an old topic, can someone just link me to an old thread?

 

Pic of truck

 

The software shows IMG ability but the site doesn't support it? Oh well. LOL! Same for avitars?  

[mnstrmdnss]

hate to say it, but if your O2's are bieng "knocked out" from an oily substance, thats not good. you might solve the problem bare minumin with a head job, getting new head gaskets, and a new set of heads, but with 206K miles,sounds like that motor has seen better days, and you might just want to think about a new motor, or one out of a wrecked truck with less miles on it, cause you could put money into a head job, but then you could throw a rod or spin a bearing down low in the bottom end!

[Ox1]

I don't believe the heads are bad. It doesn't smoke at all that I have ever noticed during startup. {valve seals} I don't know of any other reason that heads would be relavent? I am not scared of the motor at all. Sold our '88 with 260K on it after a head job at 180K. At 180 the cam showed .005" wear, timing chain/gears were tight, and bearings looked like I could get another 80 on it, so I got the heads done and put it back together with new seals and drove on! WOW! GM sure changed motor building practices! Never saw a used SB Chevy cam that wasn't almost flat. !!   That was still a good truck when we sold it with 260 on it 4 yrs ago.

 

Planning on running another 100 or so on this one. They don't give them away eh? GM trucks are NOT throw away items! And I would never bother with a junkyard motor. Did you ever notice that they ALL seem to have about 50K on them? Coincidence?

 

I very well might put another motor in this truck, now or later. But on a truck that uses only a qrt in 3000 miles or so of highway use just doesn't sound right, AND if this is the case, just fuels my fire against all this 'putor crap. (as I type this out on my 'putor eh?) But I think ya'll know what I mean.

 

It has come to my attention that we had both sides of the cat setup replaced by an aftermarket setup. I just redid the tranny and thought that it looked like one was older. ?? But I think that she is right that we replaced both.

 

Does anyone burn oil in these trucks and NOT have a problem like this? Does this sound like a real problem? Or should we be looking elsewhere? I read another thread where a fella was having troubles with an oxygen sensor on an '85 truck. Turns out it wasn't really his sensor after all, and I have to think that he is using more oil that she is. ??

[awdvkd]

You may have already done this but have you thought about a compression test to eliminate any of those problems associated with blow by or valves. Plus aren't the cats after the o2 sensors so why would they be the cause (Could be wrong but my truck has them in front).  Has it ever thrown any rich fuel mix error codes?  Unburned Unleaded fuels have a bad habit of leaving a very hard shelac finish on things and can cause spark plugs not to fire maybe this is what is happening to the o2 sensors.  Just my 2 cents, good luck

[CMNTMXR81]

Today's OBDII compliant vehicles such as his since it's a 96, have an Upstream HO2S (Pre-catalytic converter) and a downstream HO2S (post catalytic convertor).

 

Are you sure it's not black soot from incomplete combustion and/or running too rich?  If you're only burning a quart, that's piddly sh*t and pretty much normal and isn't enough to work it's way down hot exhaust piping (without you smelling it burning) and coating the sensor(s).

[Ox1]

Plus aren't the cats after the o2 sensors so why would they be the cause

 

As he said, yes it has both bf/aft units. Lovely eh?

 

I guess I mentioned the cats as fas as not having a plugged cat causing problems. I believe it is the sensor closest to the motor too. I might do a comp check this weekend.

[americanmuscleman]

I agree with what they said above.  If you know its oil on the oxygen sensor, I'd do a compression check to check for blow-by.  If things check out, you might look into new valve seals.

 

You might also scan your computer to see if your getting any error codes.