cats and O2 sensors

[mechtech]

The rear O2 sensors simply tell your computer if the cat is working. It is looking for a difference from the front sensor reading.
The front O2 sensor measures the O2 content, sends a signal to the computer, which will adjust the A/F mixture.
A bad cat could be caused by over richness, or oil burning, for sure.

 

[Matt_S]

How much oil do you use? Have you check the spark plugs? Getting a look at them might give you a better idea of what caused the cat/O2 sensor failures. Knowing what kind of car you have might help, too. I agree with mechtech that it's possible the front passenger's side sensor could have been bad, causing the failure of the cat and the rear sensor. Looking at that bad sensor, I'd say that's the most probable scenario. It looks like it's a rich mixture fouling, not oil fouling.

About the plugs, if they have the same sort of fouling as the O2 sensor (a thin black layer of carbon covering everything), I would lean toward a bad pre-cat O2 sensor on that side. If you see oil fouling (clumpy, oily buildup), I would lean toward oil burning. If you see clean plugs, you could have just had a bad cat.

 

[GoldenRod]

marcre: Please don't take this the wrong way, but you are going by some guy's testimony off ebay whom you've never met. This could end up costing you more money than if you had just bought the sensors new.

 

[marcre]

Goldenrod, I didn't buy the stuff for the sensors, I bought it for the cats and "Y" pipe. I just had those sensors put in because they were newer. They looked perfect. I understand what you are saying though. I still have my old sensors, so I will switch them out.


marc

 

[Matt_S]

One word about O2 sensors: in its service manuals, GM states that a dropped sensor is to be considered bad and cannot be used. In other words, they're very delicate. If the sensors on your new exhaust system were dropped or jarred in transit, that could be what's causing your problem.

 

[ShortBuSX]

quote:

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Originally posted by GoldenRod:
I'll even buy parts from the dealer if need be.

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Come on, youd buy an O2 sensor from a DEALER??? On a vehicle with 4 of them???

 

[marcre]

quote:

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Originally posted by Matt_S:
One word about O2 sensors: in its service manuals, GM states that a dropped sensor is to be considered bad and cannot be used. In other words, they're very delicate. If the sensors on your new exhaust system were dropped or jarred in transit, that could be what's causing your problem.

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very interesting. I was wondering about that. Thanks.

 

[marcre]

I changred out the sensor today and the CEL came back. Differerent code this time.

This time, it's PO154. Now it says my front driverside is bad. I am at a loss. Why wasn't this code present before? I know the sensors I have are compatible with my vehicle, but they are not working. I am going to change this one out tomorrow and I totally expect the CEL to come back on.

I find it hard to believe these sensors are bad. They look good(I know you can't tell from the look). It is possible they were ruined durring shipping, but that's all I can think of.

This is sooooo frustrating, any ideas why these sensors are giving me so much trouble?

I'll change the other out tomorrow and I'll let you know.

Marc

 

[brianl703]

quote:

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GM states that a dropped sensor is to be considered bad and cannot be used

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I once dropped one (that was already bad) and something inside of it came loose.

 

[marcre]

I'm thinking that maybe during shipping they got damaged. Actually, I have no idea, but that is one theory.

marc

 

[got boost?]

You can test oxygen sensors very easily, (do a google search) you need a propane torch and voltmeter. I would test all the sensors to find a set that work.

 

[marcre]

thanks for the tip.

 

[marcre]

I just replaced the sensor associated witht the PO154 code. I now have PO140 abd PO160.

I will try and get to these two sensors (sensor two on each bank, the only two I haven't replaced) tomorrow. I need to get one new sensor. This is driving me nuts. I guess all four were bad, I do not see how that can be. Baffling, very baffling indeed. Hopefully this takes care of it though.


marc

 

[marcre]

I got the last two sensors changed and the CEL has not come back on. That is nice. I have the feeling all is well again with my Rodeo.

I guess those sensors were either bad or not compatible. Either way, It seems to be fixed.

I'll post about my gas mileage in a week or so.

Thanks for all the help,
marc

 

[GMorg]

I understand the advantages of electronics, but I do miss the days when a car was a mechanical device.