Hi there. Have a bob v6 which has blown 2 sets of 02 sensors. 1st time I had the incorrect MAF sensor so install the correct one and installed 2 new sensors. They worked for the last 150 miles now it's running rich again. Measured the ect and iat. Values seem ok.

Now I'm concered about the 02 sensors.... I'm buying them up eBay 3 pin universal ones 15 quid each. Wondering if it's just the cheap sensors.

Would misfire or back fire flames damage the sensors?

People say the a rich mixture would damage the sensors But if the sensors work in the first place it should run rich so they must be burning out some how.

Any ideas that it could just be cheap sensors and I should got for the bocsch ones?

Not sure about the cheap sensors, but I have got through a couple of sensors. (Bosch LSU 4.2 ones)

I think the first one got cracked from liquid in the exhaust (fuel) which rapidly cooled the sensor that can crack them.

My second sensor died when I had a cracked cylinder barrel and the cooling system let go. I am told that there are agents in the antifreeze that they don't like.


I have started treating them as consumable.

Matt

Any Ford I have encountered used 4 wire sensors, with a 3 wire sensor you are dependant on the signal earth going through the threads and rusty bolts on the exhaust manifold.

I have made a new exhaust and have new manifold bolts earth is very good. I just might try 4 wired ones. But I have a feeling it Wont help. I noticed something rattling around in them. Looks like they have cracked too.

Whereabouts are the sensors in the exhaust? Are they too close to the head and overheating?

They are located halfway down the exhaust , actually furthervaway than the factor manifold. Can they overheat? I mean these things are designed to operate at 600 c + . I know anti freeze can kill them and silicone additives but what about actuall flames

Should be fine that far away. Mine is about 4-5" from the head ports (standard Ford 4-wire part). I know the wideband sensors can be picky about location, but I thought the narrowband ones were more robust.

If the sensors have definitely failed, then it could be thermal shock (unlikely) or excessive vibration that is causing the problem? Just a thought...

Position is important, a few degrees off vertical should be...
There´s information about correct placement.