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Oxygen Sensor & EFIE voltage
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jameslb71 Offline
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Post: #1
Oxygen Sensor & EFIE voltage
I have a question about the voltage the oxygen sensor puts out vs the voltage the EFIE adds.

I have a 2001 Grand Jeep Cherokee. Per the Haynes Repair manual. When checking the oxygen sensor. The book states that the meter should read approx 400 to 450 millivolts (0.40 - 0.45 volt). I guess this is a default for the Jeep Cherokee.

With that being known. If I set my EFIE at 100 milivolts (0.1volt) starting out. Is it true that computer will read the total voltage as 500 to 550 millivolts? (400-450 default) plus the 100 millivolts the EFIE is adding. And if this is true this would bee seen as a open loop, correct?

I'm thinking since the oxygen sensor default output it 400-450 millivolts. I should set my EFIE at a lower voltage to get a leaner mixture.

And please correct my if i'm wrong. The more millivolts the the richer the fuel/air mixture the lower the leaner.

Please confirm.

JB
06-08-2008 01:19 PM
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rpatzer Offline
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RE: Oxygen Sensor & EFIE voltage
We have a 99 Jeep Grand Cherokee and a Haynes Repair Manual. It goes from '84-'00. It talks about a variable voltage from 0-1V. Yours might be different. I think you also have a narrow band sensor.

But whatever you have, what you want to do is let the sensor read "richer" than it actually is so the ECU will see that "rich" read and it will lean out the mix. So when you are adding voltage you are achieving that "richer" signal, it would send more voltage to the ECU

Open loop is only when the sensor is cold or not working. Otherwise it should contantly be in closed loop under normal driving. BTW- when it is in open loop, it spikes rich on my AFR meter.
(This post was last modified: 06-08-2008 08:47 PM by rpatzer.)
06-08-2008 02:18 PM
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mike Offline
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RE: Oxygen Sensor & EFIE voltage
Yes, all that rpatzer says here is correct.

I'm not sure what your manual is saying there. .45 volts would be the average voltage your sensor will put out, but that is actually an illegal value for an oxygen sensor. It's always above or below that amount depending on whether the mix is rich or lean. It never puts out .45 volts during normal operation.

As rpatzer pointed out, lower EFIE voltage offsets make the mix appear a little bit richer, and larger voltages make it appear even more rich. This makes the ECU lean the mix.

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06-08-2008 02:36 PM
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rich6fam Offline
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RE: Oxygen Sensor & EFIE voltage
mike Wrote:Yes, all that rpatzer says here is correct.

I'm not sure what your manual is saying there. .45 volts would be the average voltage your sensor will put out, but that is actually an illegal value for an oxygen sensor. It's always above or below that amount depending on whether the mix is rich or lean. It never puts out .45 volts during normal operation.

As rpatzer pointed out, lower EFIE voltage offsets make the mix appear a little bit richer, and larger voltages make it appear even more rich. This makes the ECU lean the mix.
I have my 2000 Nissan Frontier 2.4L 4 cyl. set at 200MV and don't get better mileage at all. Should I go higher voltage to lean it out more or lower? This is frustrating! Should I buy a guage that shows rich and lean to know which direction I should go? If I need to go higher voltage, how high can I go?
06-10-2008 10:19 AM
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rich6fam Offline
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RE: Oxygen Sensor & EFIE voltage
I have my 2000 Nissan Frontier 2.4L 4 cyl. set at 200MV and don't get better mileage at all. Should I go higher voltage to lean it out more or lower? This is frustrating! Should I buy a guage that shows rich and lean to know which direction I should go? If I need to go higher voltage, how high can I go?
06-10-2008 12:11 PM
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mangomills Offline
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RE: Oxygen Sensor & EFIE voltage
I'm running a 2000 Jeep Grand Cherokee, 4.0 ltr. with an HHO system, map enhancer and efie. I have the efie set at .28volts now and am running a tank on it. Just waiting for results. No check engine light and the loop is closed. So this high hasn't pissed off the computer yet, and the car seems to be running normal.

Always interested in others with jeeps.
06-10-2008 12:49 PM
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rich6fam Offline
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RE: Oxygen Sensor & EFIE voltage
mangomills Wrote:I'm running a 2000 Jeep Grand Cherokee, 4.0 ltr. with an HHO system, map enhancer and efie. I have the efie set at .28volts now and am running a tank on it. Just waiting for results. No check engine light and the loop is closed. So this high hasn't pissed off the computer yet, and the car seems to be running normal.

Always interested in others with jeeps.
thank you, I'll try it today and see what happens.
06-10-2008 01:45 PM
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mike Offline
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RE: Oxygen Sensor & EFIE voltage
rich6fam Wrote:I have my 2000 Nissan Frontier 2.4L 4 cyl. set at 200MV and don't get better mileage at all. Should I go higher voltage to lean it out more or lower? This is frustrating! Should I buy a guage that shows rich and lean to know which direction I should go? If I need to go higher voltage, how high can I go?

Yes, higher voltage will make the mix leaner. You can go as high as the engine will let you. By that I mean it will throw a code when you get too high, or failing that, if you go too high, it will think the sensor is bad, ignore it, and make the mix extra rich. If that happens you'll know it by the fact that your mpg gets real bad.

In any event, if you go as high as .45 volts, you will definitely be too high. You must stay below that voltage or for sure one or both of the above sysmptoms will appear.

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06-10-2008 03:52 PM
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HerronPerformance Offline
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RE: Oxygen Sensor & EFIE voltage
If you are setting the EFIE and not getting better fuel economy, turn it down some, you can lean it out but there are other controls in place to keep it from running too lean, ie the knock sensors can detect spark knock and will add fuel.

I got to think started at .100 and going up to .200 is a sweet spot...

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06-11-2008 05:17 AM
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