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strange EFIE readings
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syncromon Offline
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Post: #1
strange EFIE readings
Hello,
What a day! This gas saving stuff sure is tiring!!
I have a 1989 Vanagon, with a conversion kit featuring a 1994 Jetta 2.0 motor, (uses the 4 wire O2 Sensor). I have not been able to find any schematics for this kit (yet). The old Bosch 02 sensor used the black wire as the signal wire (grey signal ground, 2 white wires for heater). This black wire does not send a pulsing signal tho.. it is gives a steady reading at .4V. The "signal ground" gives a steady reading of .11V. I bought this sensor on eBay, its an aftermarket splice-in type, and wondering if it is a dud?
The O2 sensor plugs in the harness, the wire colors to the computer change, and the signal wire becomes grey/black. My harness looks like it has been tampered with, another wire is cut and not in use, and another wire looks like it was added on later, (which has 12V and goes to the heater). Always fun fingering out what the previous mechanic did.
Anyway, I wired up the EFIE, hoping the black wire on the O2 sensor would be correct, and have had trouble getting a fixed setting when measuring between the EFIE white/green wires. I keep turning the pot counter clock wise and doing test drives, and I cant get it down to the .150 range Im hoping for.
It seems to fluxuate with the rmps when driving, and stays above .3V, until I slow down, then it bounces around for a bit...sometimes even goes negative. Yup...this is measuring between the EFiE green/white wires, it fluxuates with the rpms. Something is not right. The van runs about the same, mpg seems worse.

frustrated! Syncromon

P.S. wired the EFIE to my switched power for the HHO, and grounded it to the body, and the Green to O2 sensor, wite to ECU.
04-02-2008 06:31 PM
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mike Offline
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Post: #2
RE: strange EFIE readings
I strongly suspect you have an AFR (Air Fuel Ratio) sensor, not an oxygen sensor. These work on a different principal than an oxygen sensor.

The first thing you should do is get a good manual for the engine you are working on, so that you can know for sure what type of sensors you have. It will be enormously helpful otherwise as well. You can't really do mods without one.

You might try here for instructions on getting free diagrams and instructions from AutoZone.

But for sure the EFIE is either not hooked up to the correct wire, or the sensor is bad, or the wrong sensor is being used. We need to find out which one. Please get a reference for that engine, and lets start there.

Please write back and tell me what you find out.

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04-02-2008 08:43 PM
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syncromon Offline
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Post: #3
RE: strange EFIE readings
Hi Mike,

Here is what puzzles me most, The EFIE is using a seperate switched power wire, (that powers the HHO), and grounded to the body. Shouldn't the output that the EFIE is producing (testing between white/green wire) remain a fairly constant voltage when the unit is on, and independent of the O2 reading?
I want to get this setting around .150 V, but no matter how much I turn the screw (counterclockwise) the reading goes back to around .340V when driving, and fluctuates when I decelerate.*

As for my vehicle, I admit it is a pain in the bum, the engine conversion does not match any of the manuals I have found, and the company that made the conversion discontinued this kit. It has been a pain every time I need to work on it, as it is no longer stock from the factory.

I will do some more research today, and try to find some diagrams of the ECU and schematics, and other info. I replaced the O2 sensor 3 years ago when the conversion was installed, and again last week, but Im suspecting it may not be working.

THANKS, and wish me luck! Syncromon

*I have a voltmeter hooked up to watch the EFIE while driving.



mike Wrote:I strongly suspect you have an AFR (Air Fuel Ratio) sensor, not an oxygen sensor. These work on a different principal than an oxygen sensor.

The first thing you should do is get a good manual for the engine you are working on, so that you can know for sure what type of sensors you have. It will be enormously helpful otherwise as well. You can't really do mods without one.

You might try here for instructions on getting free diagrams and instructions from AutoZone.

But for sure the EFIE is either not hooked up to the correct wire, or the sensor is bad, or the wrong sensor is being used. We need to find out which one. Please get a reference for that engine, and lets start there.

Please write back and tell me what you find out.
04-03-2008 08:57 AM
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mike Offline
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Post: #4
RE: strange EFIE readings
The only time I've heard of an EFIE doing that is when it's hooked up to an AFR sensor. The AFR sensor circuit is an active circuit. The ECU is trying to pass current through the sensor and back to the ECU. The sensor is supposed to modify the current flow, and that's how it communicates to the ECU. It sounds like that .34 volts is being produced by the ECU, because the EFIE won't do that (after being turned all the way down).

The oxygen sensor circuit is passive. The sensor puts a voltage on the line, and the ECU reads that voltage level. There's no current to speak of. Whatever voltage the sensor is putting out, the EFIE adds it's voltage on top of that, the ECU reads the higher voltage, and everything behaves as expected.

If you want to verify the EFIE itself, disconnect if from the sensor, re connect the sensor to the ECU, and then watch the EFIE's voltage while driving. You'll see that it remains constant. The voltage you've been reading has been being created by the ECU, due to the nature of the sensor.

That is my theory. Please check it out. Maybe you have the first EFIE to be wonky, and it needs to be replaced. But I don't think so.

See if the above helps, and let me know what happens.

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04-03-2008 01:34 PM
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syncromon Offline
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Post: #5
RE: strange EFIE readings
Hi Mike,
Well, today I disconnected the EFIE from the sensor, reconnected the sensor to the ECU, the EFIE was hooked up to the power (red) and grounded (black) to the body, to be sure it was a good connection. The EFIE makes static buzzy noises when connecting the wiring, and when testing the white/green wires with my voltmeter...the reading was always 0.00 zero. Adjusting the screw did nothing, brand new battery in the voltmeter.
Perhaps I could like to send it back to you for further testing/analysis, and see what you think.

Im also waiting for info from the company sold the conversion motor for my vanagon, to see what mods they did to the ECU wiring. Tomorrow I will do further tests on the O2 sensor. Gas is $3.99 a gallon here, and that is my motivation!

THANKS for your help! Vince


mike Wrote:The only time I've heard of an EFIE doing that is when it's hooked up to an AFR sensor. The AFR sensor circuit is an active circuit. The ECU is trying to pass current through the sensor and back to the ECU. The sensor is supposed to modify the current flow, and that's how it communicates to the ECU. It sounds like that .34 volts is being produced by the ECU, because the EFIE won't do that (after being turned all the way down).

The oxygen sensor circuit is passive. The sensor puts a voltage on the line, and the ECU reads that voltage level. There's no current to speak of. Whatever voltage the sensor is putting out, the EFIE adds it's voltage on top of that, the ECU reads the higher voltage, and everything behaves as expected.

If you want to verify the EFIE itself, disconnect if from the sensor, re connect the sensor to the ECU, and then watch the EFIE's voltage while driving. You'll see that it remains constant. The voltage you've been reading has been being created by the ECU, due to the nature of the sensor.

That is my theory. Please check it out. Maybe you have the first EFIE to be wonky, and it needs to be replaced. But I don't think so.

See if the above helps, and let me know what happens.
04-03-2008 05:49 PM
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mike Offline
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Post: #6
RE: strange EFIE readings
When you say you were testing the white/green wires, you were testing with one probe on the white and one on the green? The EFIE never produces 0 volts unless the voltage regulator is fried, which can happen if it's wired up backwards to power for any length of time. Or if it doesn't have power at all. However, if you're measuring either the white or the green to ground, then you will get 0 volts. How were you measuring?

If you were measuring between the white and green, then the EFIE is damaged. Please send it in to me.

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04-03-2008 08:30 PM
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flyinryan02s Offline
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Post: #7
RE: strange EFIE readings
Sorry to revive an old thread, but I think my problem is similar. I have the efie all wired in as instructed.
When the key is in ACC setting, the efie voltage reads constant around 230mV on the multimeter as desired.
When the car is running, the efie voltage jumps from -400mV to like 150mV.
When driving, the efie seems to make no difference.

I believe my problem is an A/F sensor rather than O2. Is all lost or is there some easy solution?
I've been working on this forever since there seems to be little to no technical information available for a 2002 CR-V.
What do I need to do?
07-16-2013 07:40 AM
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