Am thinking about replacing the upstream o2 sensor on my Vulcan to see if it helps my mileage, is that the one i want to replace and how easy it to change?
When the O2's get bad beyond a pre sent threshold, they will trigger a codeI have no codes showing as of now was just thinking with the 126k miles on the stock ones it would be something due for a maintenance item, but if its still good i will leave it.
How sure is it that the codes will show when the o2 sens is bad ? Is it possible to have a failing sensor with no code?
Conflicting opinions are relative to the situation. You get a 10 year old+ car with over 100K, most people are not going to put unnecessary money into the car if they can help it. Even most of the auto thieves at the quick lube shops and such don't normally try to sell you O2 sensors unless the code light is on. Sure i will agree, the sensors do degrade. So does EVERY other system on the car. So a car withSee we are getting conflicting responses here, some posted by those who have never tasted the dark side of what happens when they go wrong. I deal with catalytic converters all the time, and believe you me, most of those that fail are the result of O2 sensors that also failed, but never set codes. The O2 sensors don't set codes until they because almost completely non-responsive. May faulty O2 sensors will output descent response times and signals that are within specs, and yet they are not accurate at all.
The computer does not reject the sensors or even alert you that there might be a problem until you get around 12% off on the Long Term Fuel Trims, yet my experience has taught me that catalyst degradation begins to occur between 3-5%. An O2 sensor costs you between $60 - $80, is not that hard to replace, if its not left in there too long, can improve the gas mileage and performance of the vehicle, and helps protect the catalytic converters from being damaged or plugged.
If the catalytic converter fails, it can cost you up to $800 to have it fixed with aftermarket replacements (depending on vendor and whether or not you have it professionally installed), plus you will still have to get the O2 sensors replaced. Many people have plugged EGR passages and experience EGR problems. I have never had a EGR problem, but then again I also replace my O2 sensors on a regular basis.
Hers how it works. The O2 sensor element gets coated with deposits, which can be sulphur compounds, chemicals from the oil, carbon, antifreeze, etc. These deposits reduce the sensors active surface area, which causes a decrease in the voltage output. The computer cannot tell the difference between the low voltage from a contaminated sensor and a lean condition. So the computer will increase the injector pulse width to compensate, which will produce the desired effects. The lower oxygen level will cause the voltage to increase even if the sensor is contaminated. However this rich condition will begin to cause additional deposits to form, which has the same effect on the catalyst, the sensors, and it causes carbon deposits in the combustion chamber, EGR passages, etc. All of this begins to take its toll.
If you want to wait until the sensor sets a code, its your car, but some of the damage that is done cannot be reversed. Using an injector cleaner or a product like Seafoam does not restore catalyst function, nor does it undo scuffing and scarring to the cylinder walls due to carbon deposits around the rings.
The computers parameters for acceptable O2 sensors in my opinion are way too lenient. The computer should begin warning you of problems at around 6%, not 12%. In my opinion, paying $60 to $80 for a new sensor is cheap for having a nice car that will be reliable and trouble free for years, as opposed to leaving it in there and having to spend major money fixing failed emission components or having to get another car simply because the old one has become too costly to repair. An once of prevention is worth a pound of cure.