April 15, 2001

What's wrong with my car now?!?

April 15, 2001

Did I mention how thrilled I am to be a Chrysler owner? The Egulphymobile is on the fritz yet again, this time for another O2 sensor, prompting the Paperless One to ask the obvious: what's the deal with O2 sensors anyway?

From the O2 sensor FAQ:

Many Oxygen sensors are replaced that are good to excellent. Many people don't know how to test them. They routinely last 50,000 or more miles, and if the engine is in good shape, can last the life of the car.

What does the O2 sensor do?
It is the primary measurement device for the fuel control computer in your car to know if the engine is too rich or too lean. The O2 sensor is active anytime it is hot enough, but the computer only uses this information in the closed loop mode. Closed loop is the operating mode where all engine control sensors including the Oxygen sensor are used to get best fuel economy, lowest emissions, and good power.

Should the O2 sensor be replaced when the sensor light comes on in your car?
Probably not, but you should test it to make sure it is alive and well. This assumes that the light you see is simply an emissions service reminder light and not a failure light. A reminder light is triggered by a mileage event (20-40,000 miles usually) or something like 2000 key start cycles. EGR dash lights usually fall into the reminder category. Consult your owners manual, auto repair manual, dealer, or repair shop for help on what your light means.

How do I know if my O2 sensor may be bad?
If your car has lost several miles per gallon of fuel economy and the usual tune up steps do not improve it. This *is not* a pointer to O2 failure, it just brings up the possibility. Vacuum leaks and ignition problems are common fuel economy destroyers. As mentioned by others, the on board computer may also set one of several failure "codes". If the computer has issued a code pertaining to the O2 sensor, the sensor and it's wiring should be tested. Usually when the sensor is bad, the engine will show some loss of power, and will not seem to respond quickly.

What will damage my O2 sensor?
Home or professional auto repairs that have used silicone gasket sealer that is not specifically labeled "Oxygen sensor safe", "Sensor safe", or something similar, if used in an area that is connected to the crankcase. This includes valve covers, oil pan, or nearly any other gasket or seal that controls engine oil. Leaded fuel will ruin the O2 sensor in a short time. If a car is running rich over a long period, the sensor may become plugged up or even destroyed. Just shorting out the sensor output wire will not usually hurt the sensor. This simply grounds the output voltage to zero. Once the wiring is repaired, the circuit operates normally. Undercoating, antifreeze or oil on the *outside* surface of the sensor can kill it.

Will testing the O2 sensor hurt it?
Almost always, the answer is no. You must be careful to not *apply* voltage to the sensor, but measuring it's output voltage is not harmful. As noted by other posters, a cheap voltmeter will not be accurate, but will cause no damage. This is *not* true if you try to measure the resistance of the sensor. Resistance measurements send voltage into a circuit and check the amount returning.

How long should a catalytic converter last?
Since most catalytic converters are covered by warranties that surpass any other warranties, even the auto manufacturers expect them to last at least 7 years (and a day).

That having been said, the Egulphymobile, a car of less than four years, has gone through at least four O2 sensors, and had to have the catalytic converter replaced as well. I must say...I am disappointed in this so-called North American craftsmanship. The more that goes wrong with the first North American car I've ever owned, the more I like my Japanese car, although it may have something to do with the fact that Americans never came up with "IRON CHEF" as well.

First of all, let me state that the Paperless One does continue to feed premium gas to the Egulphymobile, even when it costs upwards of 80 cents a litre, so don't start telling me that it's the fuel. Second, Pioneer Petroleum and their methanol crap gas are also banned from the Egulphymobile!

Anyway, the Paperless One would love to hear from you if you have any car horror stories similar to mine, or if you are working on the formation of an Ontario chapter of the Chrysler Lemon Owners Group. It appears that I may need to join, as I'm not accustomed to having so many things go wrong with a vehicle.

I'll post horror stories and guest columns in the near future - the Paperless One needs a week off sometime.

Go Leafs go!