Asking for 0² sensor knowledge.

My old F100 doesn't have this fancy stuff, but my 20yr old car does. My area began emission testing last year. The car passed with flying colors. Yesterday it passed again, but the results were very different this year....mainly the CO%.

The standard is 1.20: High RPM last year was 0.01, this year 1.08. Low RPM was up from 0.03 to 0.13.

The HC was a bit different too:

standard is 220: last year at High RPM the reading was 45 and 47 at low RPM. This year 17 at High and 100 at Low

The other test results are similar to last years results. This emissions testing is a new ballgame for me, so I'm at a loss to know what these results are pointing to?

During a 4500 trip last fall I had to use 10% ethenol gas for a few tankfulls. My mileage dropped almost 3mpg and when I got home I had a code, O=8D=B2 sensor 'not ready'. I cleared that code and it's not showed up since.

I pamperwell-maintain this car as it's my get-out-of-town ride. The F100 is daily drive ride.

The Texas Clean Air website points to the sensor having a problem. My OBD had the sensor code, but it hasn't returned, so?

The car passed but I'd feel better about being closer to the first years result than yesterdays results. Any info would be appreciated. Thank you....

Dave S(Texas)

Reply to
putt
Loading thread data ...

.=2E.

Dave,

10% ethanol is all I can get here in Minnesota for the past 3 or so years, so you can be pretty certain that the use of ethanol in your vehicle didn't damage anything. Your decrease in mileage with that fuel is as expected. (BTU per gallon of ethanol is lower than regular gasoline)

When was the last time you replaced the oxygen sensor? If never, and the car has more than 60,000 miles on it, you might as well just replace the sensors.

The oxygen sensor in a production vehicle is typically considered a "narrow band" oxygen sensor. These sensors are only able to signal how close to "perfect" the oxygen level is. So one voltage will be too rich, the other voltage means too lean. The engine computer monitors the oxygen sensor and adjusts the fuel ratio when in closed loop many times a second.

When the sensor tells the EEC that the engine is running rich, the EEC pulls back fuel timing to decrease the amount of fuel injected. Then when the sensor says things are lean, the EEC adds more fuel. The EEC is never able to do better than add a little fuel till it's too rich, then take a little fuel out until it's too lean. This flip and flop of the engine management system is keyed directly to how fast the oxygen sensor can itself sense too rich and too lean.

As oxygen sensor is constructed with a platinum coating. Over time this coating becomes damaged or oxidized and hinders levels at which the sensor will respond to rich or lean conditions. This causes the engine computer to get the engine too rich, before it's told it's rich, and too lean, before it's told it's lean. This has a noticeable impact on fuel economy of your engine. Older OBDI computers often could only fail an oxygen sensor if the sensor gave signals off scale, or didn't ever change. Current generation OBDII engines use dual oxygen sensors and they have response timings they expect the sensors to perform within. Once they stop performing within those timings, the check engine light will be triggered.

The point of all of this is, if you haven't replaced your oxygen sensor in a number of years and a number of miles, there is no question your care will perform better if it is replaced.

Reply to
Mike H

Thanks Mike for that education. Car is OBD1. The answer to your question: never. I'm positive it is the factory installed piece. I've read 'somewhere' those things should be replaced every 30K miles. So at

93K....this would be the time!! lol Any trickery to getting this piece loose? I very much appreciate the help...everyone! Thanks

Dave S(Texas)

Reply to
putt

...

An OBD1 car is a little easier on oxygen sensors as it should only have at least one, and at most two oxygen sensors. If there are two you should replace them both. Make sure you use the special socket as you'll need a lot of leverage to get the sensor loose. Since they sit in the exhaust system, ahead of the converter, they are exposed to extreme heat as well as moisture. This essentially fuses the threads of the sensor to the bung in the exhaust pipe that it's thread into. Even with anti-seize it can take a lot of effort to remove.

Unfortunately they don't usually put those things on in a spot that makes it easy to get a impact on it. I've found a 1/2" drive wrench with a two foot length of conduit over a breaker bar can often get them loose.

Reply to
Mike H

Only 1 sensor for the system. I assume this removal should be done on a cold exhaust? Is using a penetrating fluid ok? I use the Rust Eater brand penetrating spray for getting parts loose.....Thanks for the link!

Dave S(Texas)

Reply to
putt

Yes, you want the exhaust cold. Though if you have access to co2 or some similar type of cooling agent, hot exhaust, then cool the sensor rapidly might make it easier. But rubbing up against hot exhaust isn't fun.

PB Blaster, Rust Eater, anything will help. I'd suggest soaking it a couple times a day for a couple days. Maybe bang on the pipe with a hammer a few times close to the fitting just to loosen things up. A new sensor might not like the penetrating fluids, but the old sensor doesn't care anymore.

Reply to
Mike H

What does that mean? Anyway, cold pipe and hope it comes loose. I know a new sensor comes with a glass-bead anti-seize compound. I wonder if that stuff was used back at the factory in '87? Odds of that? Thanks!

Dave S(Texas)

Reply to
putt

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.