Change Oxygen Sensor?
The truck has less than 50000 miles and is in perfect shape. BUT, the exhaust smells pretty bad hot or cold. So I don't think the 02 sensor is working correctly. The truck is rated at 8600 lbs so there is no CAT present but about half way down the exhaust there is a junction where the 02 sensor is.
Will a sensor go bad without a CEL?
Will a OBD1 test find a fault with the 02 sensor even if there is no CEL?
Or is it just better to change it anyway just because of the age?
Thanks ahead of time.
Could you elaborate on this statement: "about half way down the exhaust there is a junction where the 02 sensor is." Halfway down where? It should be near the engine.
The F250/350 trucks have a dual y-pipe that ends in a flange where the converter would have attached. There is a small cross-over pipe between them, that is where the O2 bung is mounted.
O2 sensors do deteriorate over time. But we need to have a better idea how your exhaust is configured. A few photos would help a lot.
That is what I was writing about.
As for the exhaust I am not sure the answer. The owner says the exhaust has not been changed since he bought it. This is/was a one owner truck and I know him pretty well. It was parked in a garage next to the camper he and his wife used a few times a year. Which is why the low miles.
If there were CAT's were would they be placed on the exhaust? There is nothing but the muffler when it comes to the exhaust, from the headers to the end.
The H-pipe looks like this:

The converter bolts to the flange on the end of the H-pipe. Hard to say why yours is missing the converter.
Going back your issue, the O2 sensors appears to be located in the factory location. Yes they can deteriorate with age. Yes, OBD-I will report a lean or rich error code. Yes, there can be a stored code without a Check Engine Light on.
But, if the CAT is missing then I guess the smell would continue even with a new 02 sensor.
Again, thanks for all the help.







