Re: Is it possible to clean the OS2 sensor

Thanks Tim, On which of the wires should I connect the voltmeter? There are four wires, one of them is connected to the ground (-). What are the other three for? ( I assume two are for heating the device and one for measuring ) Is it possible to disconnect the sensor and drive for a few miles in order to find out if the sensor worsen the engine behavior?

BTW I have a mazda portage 1999 1.6 liter.

Ariel

Depends what it is dirty with. If it just has carbon on it, running the engine at 3000 RPM or so for a few minutes would likely clean it off fairly well. If it's got something else on it, it's unlikely that it could really be cleaned.

You mentioned this is a '99 - generally on '96 and later vehicles with OBD II, a problem with the oxygen sensor should set a trouble code and turn on the Check Engine light..

Although an O2 sensor code may be indicated, the problem in not in the sensor 99% of the time, it has merely become contaminated by a fuel/air ratio glitch. Find out why it is being contaminated, rather than changing or trying to clean it, WBMA. It will simply fail again shortly. Unless it is burned up, once you find the defect that is causing the fuel/air ratio to be operating outside its design parameters and have it corrected, the sensor should clear up and be OK.

mike hunt

Robert Hancock wrote:

At first, the problem was with the MAF sensor. I cleaned the sensor

That's not really the sort of problem that would be likely to damage the oxygen sensor (not many would, except maybe for coolant getting sent out the exhaust). The lack of a trouble code isn't an absolute guarantee that it's working, but on an OBD II car, it's probably safe to assume that it is.

You say the engine is shaking at idle speed - I'm assuming you don't mean normal engine vibration but an irregular vibration indicating a misfire. That's not the sort of thing a bad O2 sensor normally causes, that's usually something ignition related.

Well, all depends how much work you want to do. The O2 sensor creates a voltage potential across it based on how much oxygen is in the exhaust.

lots of oxygen = rich = high (relative) voltage not much O2 = lean = low (relative) voltage

So a rich condition should create a potential of around a 0.9 of a volt, lean around 0.1 of a volt, and the correct mixture somewhere in the middle.

If you hook some wires in parallel with the sensor and run them to the passenger compartment, then hook a digital voltmeter up to the wires you can watch the values under various driving conditions and see what the readings are, i.e. engine under load accelerating up a steep hill = rich, engine coasting down a hill, foot off the gas pedal = lean, driving down a flat road = in the middle.

Just make sure you don't actually disconnect the O2 sensor. It has to keep sending its signals to the computer.

Cheers, Geoff Glave Vancouver, Canada

This is backwards. Lean = "lots of oxygen." Rich = "low oxygen."

True except that there is no such ting as "correct mixture somewhere in the middle." O2 voltage should always be toggling high and low.

-That- indicates correct mixture control.

There's nothing wrong with disconnecting the O2, connecting directly to it and creating lean and rich conditions and watching for the coresponding voltage changes.

oops! Right you are. "Sorry about that, Chief." (I should really stop writing usenet posts at 2am).

On a vehicle with a computer how would you create "lean and rich" conditions? Impair the air intake somehow? Or ??? It's not like you can adjust the mixture screw.

Cheers, Geoff Glave Vancouver, Canada

To create a lean mixture, just create a vacuum leak by disconnecting a vacuum hose (e.g., brake booster). To create a rich mixture, inject propane into the disconnected hose.

Another method since vacuum leaks can create confusing results or running problems on MAF sensor equiped vehicles is to; Disconnect the O2 sensor, connect your DVOM directly -to- the O2 sensor, back-probe the harness lead for the O2 sensor (the wire that goes back to the ECM), with an aligator clip or other suitable device, then hold that O2 lead in one hand and alternately touch battery + and battery- with your other hand (your body acts as a resistor). Touching B+ sends a rich indication to the ECM, the O2 voltage should drop accordingly. Touching B- sends a lean signal to the ECM, the O2 voltage should rise accordingly.

Wow, I haven't heard that one for years! Works fine though. Thanks for reminding me.

No. If you need a new one just buy one. You didn't state how many miles you have on your car, but since it has enough miles to get the MAF dirty, you possibly have enough miles to need an O2 sensor.

OEM Front $99.99 OEM Rear $169.99 Universal Front $49.99 Universal Rear $59.90

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