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EFIE voltages
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mec Offline
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Post: #1
EFIE voltages
I have the EFIE installed and notice something I think is wrong. With the efie off and the engine running, the voltage from the O2 sensor (green wire) fluctuates up and down between .2 and .8 volts. When I turn the efie on the voltage from the green wire to ground almost stops fluctuating and stays at about .755 volts plus or minus. The white wire stays at about .987 plus or minus.

Is the voltage fluctuation supposed to stop when the efie is on? What is wrong?
03-18-2008 05:59 PM
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mike Offline
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Post: #2
RE: EFIE voltages
Definitely not. The voltage should be fluctuating. However, it sounds like you have the EFIE set way too high. Please set the EFIE to about .150 volts and try again. It sounds like you have a circuit board, or basic model, so measure between the white and green wire and adjust the potentiometer until you have .150 volts. Then try again with the same tests you've already done.

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03-18-2008 07:46 PM
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mec Offline
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RE: EFIE voltages
OK Mike, I reset the voltage between the white and green wires to .145 volts. The green wire to ground fluctuates between .2v and .8v. The white wire to ground is still way too high. It's fluctuating between .81 and .88. This is with the engine running at idle.
03-20-2008 12:08 PM
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mike Offline
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RE: EFIE voltages
Something is wrong, and we must find out what. If green wire to ground is .2 - .8, that is what I would expect. But then I would expect to see those same numbers, plus .145 at the white wire. You should be seeing .345 - .945. I realize that exact numbers are not useful when the voltage is changing like that, but I used them exactly so you could see how I arrived at them.

Something has to be wired incorrectly if you're not getting those numbers. Please review the Installation Instructions, and in particular, verify that your install matches the wiring diagram. You might also re-take your measurements at the white wire, and make sure you have a good ground for it.

Let me know if that helps (or not).

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03-20-2008 01:15 PM
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mec Offline
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Post: #5
RE: EFIE voltages
I checked everything again. I hooked up 2 meters so I could look at the green wire and white wire voltages at the same time. I see normal fluctuations when the efie is off. When I turn on the efie the voltages fluctuate normally for maybe 30 seconds and then both creep up to: Green wire .740 average, White wire .880 average. I was checking the green wire first every time with one meter and didn't realize it was creeping up too. If I turn off the efie off things fluctuate normally again. When I turn the efie back on after a few minutes green and white wire voltages fluctuate normally for aprox 30 seconds and then creep up again. This is getting strange.
03-20-2008 02:16 PM
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mike Offline
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RE: EFIE voltages
Dumb question: When hooking up the EFIE, did you cut the oxygen sensor signal wire? You're supposed to cut it, and the green wire connects to the sensor end, and the white to the ECU end. It kind of sounds like the 2 wires are connected somehow. Is this possible?

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03-20-2008 02:28 PM
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mec Offline
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Post: #7
RE: EFIE voltages
Nothing seems dumb right now. Yes, I cut the wire. I cut the other wire first, and then realized it wasn't the one that fluctuated. I reconnected it, soldered it, and then cut the wire I'm using now. I can see the efie is working in that there is a voltage difference between the green and white wires equal to the offset voltage. I just can't figure what is pulling the voltage up.
I hot glued the efie board onto a larger board that fits nicely inside a plastic box. I ran 2 lines of hot glue and then stuck the efie board on top of the other board. Could I have damaged the efie doing that? The glue is non conductive.
03-20-2008 03:03 PM
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mike Offline
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Post: #8
RE: EFIE voltages
No, I don't think you can damage the board that way. I wouldn't worry about that.

Do you get a check engine light after your voltage creeps up? Another possibility is that the ECU has determined that your oxygen sensor signal is incorrect, and is ignoring it, and when it does this, it runs extra rich. Your voltages indicate that there is a very rich air/fuel mix and that the ECU is not using the sensor's data.

The only trouble with that theory is that with the low EFIE setting you're using, that should not be possible. Just because I can't think of anything better at the moment, try running the EFIE at about .075. Even lower if you can get it. Doesn't have to be exact. It's pretty loosey-goosey when you get down that low. See if the ECU will buy a lower setting.

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03-20-2008 04:46 PM
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mec Offline
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Post: #9
RE: EFIE voltages
I have not gotten a check engine light during my testing in the driveway. I'm not driving around with the efie on though. I ran the efie at .075 and there are voltage swings but they are in the higher range. Such as, .6 .7 .8v, the rate slows down and becomes more erratic. I turned the efie as low as I could get it to go, .015v, and there are normal voltage swings. When I slowly turn it up the voltages slowly creep up and the swings get smaller. At about .04v the pull up is noticeable and the swings run in the .4 to .8v range.
03-23-2008 02:29 PM
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mike Offline
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Post: #10
RE: EFIE voltages
I've never heard of an ECU detecting a problem with that small of an EFIE adjustment. But it appears that that's what's occurring. The higher voltages you see is the oxygen sensor saying the mix is rich. And that's bad for fuel mileage.

Try setting the EFIE low enough that it doesn't trigger the higher voltages. Below .04 volts. Try driving a tankful like that and see what mileage you get. It's also possible that after driving for a tankful, you will be able to raise the EFIE further without triggering the rich condition. ECUs "learn" new conditions and adapt to them after a period of time.

I suspect you're going to have to get into adjusting your other sensors as they seem to be tipping off the ECU that we're adjusting the oxygen sensor signals.

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03-23-2008 03:36 PM
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