oxygen sensor and leaded fuel

I've just been reading other threads about O2 sensors - and I'm deeply impressed by the expertise of Rick Anderson and others on threads like this one
http://www.naxja.org/forum/showthread.php?t=909131&page=2&highlight=oxygen+sensor

Here's my question... I have a 1993 XJ 4.0 litre. I knew when I bought it (new) that I would be using it in foreign countries which did not have unleaded fuel. So I had the cat removed (I still have it, brand new...) and a through-pipe fitted. But I left the O2 sensor in place (the '93 XJ only has one, upstream of the cat). I knew it would probably be affected by lead; but the advice I got then was that the engine systems would run OK (on default settings???) . Anyhow, 14 years and 100k miles later, the engine still runs sweetly, and my gas consumption doesn't seem too bad.

I thought however that as I am now back in unleaded-fuel-land, I should probably replace the O2 sensor. But then I found out how expensive they are in UK! So the question is - will my sensor have been affected, and if so how, by running for about 8 of the past 14 years on leaded fuel, some of it pretty low-octane? And will this have had any other consequences for the computer-management systems or the engine itself. Should I change the sensor even if it costs £££? Or should I just continue running things as they are, on the grounds that "if it ain't broke..." ?

br1anstorm

"If it ain't broke..." Unless you start noting failing fuel mileage, I'd not worry about it.

If anything is happening, it would be that the TEL (tetraethyl lead, used as an octane improver more than anything else) would be depositing lead on the sensor element. It could eventually clog it - but so could carbon from running too rich in the first place (which also clogs up the sensor tip.)

Fuel octane should not affect your HEGO sensor in any negative fashion, unless something about it starts royally throwing off your fuel/air mix (if it throws it off in the "rich" direction, you could have trouble with carbon deposits. It it throws you mix too "lean," you could potentially end up overheating and killing the sensor - but you'll have larger problems to deal with if that happens.)

So, don't worry about it until it does break down. "Spec" service life on a HEGO sensor is ~80Kmiles, but I've seen them last much longer (I'm finally going to change the original in my 88 - at ~280Kmiles... It's getting old and not responding very quickly...) Don't worry about it until the time comes.

And, since TEL was still in use when the HEGO sensor started being used, I'd think it would be at least fairly tolerant of lead buildup...

HEGO - Heated Exhaust Gas Oxygen (sensor)
TEL - TetraEthyl Lead. What makes "leaded" fuel "leaded."

Thanks, 5-90, for the reassurance. I'm hoping (and the evidence seems to suggest) that the sensor hasn't been too badly affected by lead buildup. And for what it's worth, I don't think the engine has been running rich - emissions have been well within the UK/European limits in tests since I returned from foreign parts.

By the way (and this strays a little off topic), did you hear about the trauma here in UK recently when thousands of cars were filled up with petrol contaminated with silicon(e)? I wasn't a victim. But cars were dying and seizing up all over the country, their O2 sensors wrecked. Only after millions of gallons of fuel had gone out and been sold through supermarket filling stations did it emerge that a huge quantity of silicon(e) had been found in a distributors' storage tank. Apparently small amounts are used as an anti-foaming additive in diesel, but not normally added to petrol. The compensation claims are only just beginning!

br1anstorm