high emissions - O2 sensor replacement?

beerhunter · Jan 17, 2018

Hi

I'm currently trying to fix various issues with my truck to get it on the road. One of the problems is high emissions.

I suspect this is in part because the previous owner didn't drive it much, and what is needed is a good long motorway run.

However, I can't do that until it passes its MOT test. I understand worn-out O2 sensors can cause rich running. Is it worth me replacing mine, to try to get the emissions down?

Many thanks

2trux · Jan 17, 2018

One thing to check, pull the exhaust apart between the Y pipe and the catalytic converter to make sure it hasn't been gutted. I tried most everything to get my son's BII to pass emissions with no joy until I checked the cat and found out it was empty. A new cat and he passed with no problem.

beerhunter · Jan 18, 2018

Thanks - de-catting (as they call it here) is fairly common (though probably illegal) but I wouldn't have thought to check. Thanks for the tip.

RonD · Jan 18, 2018

O2 sensors should be replaced every 150k miles at least, 100k is specified
They use a chemical reaction like car batteries, so do wear out just like a battery does.

Low milers can make mileage a moot point as the O2 sensors can be fouled if engine was not heated up fully each time it was started.

Thermostat needs to be 190-195degF, some use 180degF which will raise emissions levels
If temp gauge shows just below 1/2 after full warm up then t-stat is OK, if it only gets to 1/3 then most likely it has 180degF or leaking thermostat.

Run a can of Seafoam or similar injector cleaner in the gas tank, that will help clean injectors and cylinders of carbon

adsm08 · Jan 18, 2018

Which gasses are out of whack? There are 5 emissions gasses, and one or another being high or low mean different things.

beerhunter · Jan 22, 2018

Unfortunately, the previous owner didn't keep/pass on the detailed breakdown. I'll have to get it re-tested and see what's what.

Thanks

55trucker · Jan 22, 2018

If you suspect that the cat may have been gutted give them both a light rap with a small hammer, if the sounds you hear are a dead thud the cat is still full, if the sound has a dinging echo to it then the cat will be hollow.

ricardoguitars · Jan 22, 2018

Depends on what gases are giving trouble, that will give you an answer of where the problem lies. Have it rechecked and post the results.

high emissions - O2 sensor replacement?

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