Testing oxygen sensor

Can you give us any specifics about your vehicle such as make, model, year, engine, etc.?

It doesn't really matter. Almost all oxygen sensors do exactly the same thing and work on exactly the same specifications. I did a google search for "testing oxygen sensor" and it came up with 93,700 hits. the 8th hit was this:

Try letting your fingers do the walking.. There is plenty of material out there that will answer your questions with the least amount of information to find it.

-Bruce

I think one difference is that because they have to be hot to work at some point electric heaters were added so they could begin to work sooner after the car is started.

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You are correct but that is independent of testing the o2 sensor and how it functions.

The information I requested will tell me the likelihood of a faulty oxygen sensor illuminating the MIL. Just about any obdII vehicle will turn on the MIL if there's any problem with the O2.

I can tell you any OBDI or OBDII vehicle will turn on the MIL if there's any problem with the O2 sensor.. I dont' think you've told anyone anything new.

I thought the reason for the heat coil was to burn the crap off the sensor to lengthen it's life.

Did you do the basics first:

1. Does your car drive normally? I.e., is the engine misfiring or the trans slipping?
2. Does it engage all four forward gears?
3. Any chance brakes are staying applied?
4. Is the torque converter clutch operating properly? (I'm not sure if this car has one.)
5. Proper amount of air in the tires?

What was your fuel mileage drop? This will help me get an idea of how serious a problem this might be.

Nope, its to heat the sensor up so that it begins working quicker after a cold start. Getting the car into "closed loop" mode ASAP lowers emissions a LOT.

I am a MPG nut and always have been. I calculate it for each tank and keep records. Also I am the only driver. The sales tag specification for the vehicle (I still have it) is 24-city and

30-highway.

For years I could get 30-32 in the city and 33-35 in the country. Recently the city MPG has dropped to 27 and I rarely use it cross country anymore.

Now obviously I have little to complain about except that I am just very curious about the change.

The answers to your questions are all non-indicative of the item being the cause as stated below.

No. The vehicle drives like new.

Yes, and I constantly watch the shift points and they havn't changed.

No

Yes it does and third gear lockup is as 42 mph as always. There is a puzzle in my mind about whether or not there should be a second gear lockup but I can't detect it happening.

Always as specified on the door post. 30lbs

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page is bad ( spelling & grammar errors ), no diagram. This is muchbetter.

Hmm.. as long as you think exaust is an acceptable spelling for exhaust, then that's fine, your page is better. =o)

Both pages say during open loop, the preset mix will be too rich. I don't believe this ; [i] when my 1990 honda F20A engine is cool ( just started ) @700rpm, my hand put @ 1" from exhaust gas gets only water vapour, no soot. [ii] cat-convertor's platinum cannot oxidise CO / hydrocarbon to CO² / H²O without enough oxygen present

, & this is why cat -convertors have oxygen sensors. So engine designers have no reason to want the preset mix too rich ( i.e. exhaust gas has no oxygen left ).

The mixture will always be a bit richer during open loop, since the mixture control is not as precise, and running the engine too lean would cause it to run poorly or even be damaged, therefore they err on the rich side. The engine would have to be running very rich to produce visible soot.

The catalytic converter cannot oxidize any pollutants until it heats up anyway, so this is not a major problem. In newer models, the manufacturers are trying to make the system go into closed loop as fast as possible and warm up the converter as fast as possible.