"New" oxygen sensor has soot with discolored threads.

[joshhemming]

I just received a "New, in the box Bosch Oxygen Sensor" from an online parts company which has a 99.9% positive feedback record at Ebay. It arrived in the Bosch box (inside a larger plain box) and looks fine. Except: The threads and hex bolt are slightly discolored and the probe which fits inside the exhaust pipe had some black soot on it.

My question is: does Bosch test each O2 sensor they manufacture by exposing the probe to some funky exhaust? That could explain the small amount of soot.

The other explanation is they sold me a used/returned sensor while claiming it's brand new.

My second question: is there an actual test for O2 sensors on 93 Aerostars 3.0L? My van had 90K on it when I bought it, and now has 172K. I don't think the sensor has ever been replaced so I'm sure it's due anyway. This is the sensor under the van, just before the Cat Converter.

 

[BrooklynBay]

Return it immediately before they say that it's past amount of time to return it. They sold you a used one. You can check the signal with a high impedance voltmeter directly on the sensor, but not through the EEC-IV system. OBD-II on 96-up allows you do graph the signal with a scanner.

 

[Joe Dirt]

Then order a Motorcraft from rockauto.com and call it good...

 

[joshhemming]

I did return it and they quickly sent me a replacement, this time with no soot on the probe.

After spraying the old one with PB Blaster I used a long-handled 22mm combination wrench to remove it. The new Bosch, pre-coated with anti-sieze compound, threaded in easily.

I had thought about buying one of those special O2 Sensor deep well sockets with the slit in the side for the cable but I don't think there's enough clearance between the sensor and the bottom of the van for it to fit. Anyway, the combo wrench worked fine.

I don't know if the old one was bad or not but since it had been in there for at least the last 80,000 miles, and possibly the entire 172,000 miles, I figured it was a good idea to replace it.

 

[BrooklynBay]

You're lucky to get a replacement part. Did you have to pay an additional shipping charge? There is enough clearance to get a regular oxygen sensor socket on it. OTC makes an extreme heavy duty model which I think has a lifetime waranty. It's not cheap (maybe $40-$50), but it will last longer than most cheap versions. It has an extra metal band welded onto it to increase its capacity.

 

[joshhemming]

The original purchase had free shipping. I paid about $3.50 to ship it back to Utah by 1st Class Mail, and they shipped me a new one with no add'l shipping charges. So even with the return I was out a total of $33.50, vs. (I think) $47.99 at AutoZone or O'Reilly. And if I recall correctly, neither of those two had the exact replacement, with the 10" cable. All of theirs which supposedly were for 93 Aerostars had much longer cables which could cause problems under there.