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Downstream Sensor problem?
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mtnhillsman Offline
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Post: #1
Downstream Sensor problem?
05 nissan altima 2.5 liter

6 series-cell electrolyser putting out 1.4 LPM

2 oxygen sensors, one before Cat, one after Cat. I installed an EFIE on the first sensor and am still getting the same mileage. Tuning wise I havent put a meter to it but its the efie from Eagle Research, 15 turn adjustment, I started at 3 turns and bring it up 3 turns at a time every 15 miles or so. I am using the onboard mpg indicator in the dash and usually reset every 15 miles or so and make adjustments. I have found no difference in mileage for any of the settings, nor does the CEL trip when its turned full lean. I was at first unsure i had the correct wire, now I'm positive, stripped each wire, removed the EFIE from teh cirucit, and put a voltmeter to each wire, while gunning the throttle 2 of the wires showed static voltage, 2 of them jumped by barely half a volt, and the 5th wire would move a good 2 volts each time i gunned it. Oh right, yeah its a wideband sensor. I have 2 EFIE's i have tested the same way above, the one from eagle research for the narrowband sensor, one from Magnum Tuning for the wideband sensor.

I have found that my mileage is SLIGHTLY higher overall, it seems to be much higher at slow speeds, 35-45 mph ill see 35 - 38 mpg, the moment i get on the highway it drops back to normal which at 70 i always got very close to 30. Now im seeing closer to 31 on average.

So, heres my thoughts, After thuroughly reading Mike's Tuning for Mileage post I was thinking it was the MAF sensor, i thought maybe being an 05 the ECU was a little more intelligent and is not allowing the mixture to go lean when it detects all this air coming in the intake. This theory would support my mileage gains at lower speeds. Of course I never really checked my mileage at "low speeds" in the past(prior to HHO) so i could be way off there. It does seem excessively high at low speeds though.

I then read some posts that people ran into the downstream sensor also supplying the ecu with data making the single EIFE useless. I figure this is a possibility.

One thing came to mind: has anybody tried just unplugging the 2nd sensor?? I think im going to try that tomorrow. I just thought even if it trips the CEL who cares as long as ur still in closed loop...If it works just run it until inspection time.

any thoughts on this or my setup??
(This post was last modified: 01-22-2009 06:51 PM by mtnhillsman.)
01-22-2009 06:45 PM
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John Sargent Offline
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Post: #2
RE: Downstream Sensor problem?
(01-22-2009 06:45 PM)mtnhillsman Wrote:  05 nissan altima 2.5 liter

6 series-cell electrolyser putting out 1.4 LPM

2 oxygen sensors, one before Cat, one after Cat. I installed an EFIE on the first sensor and am still getting the same mileage. Tuning wise I havent put a meter to it but its the efie from Eagle Research, 15 turn adjustment, I started at 3 turns and bring it up 3 turns at a time every 15 miles or so. I am using the onboard mpg indicator in the dash and usually reset every 15 miles or so and make adjustments. I have found no difference in mileage for any of the settings, nor does the CEL trip when its turned full lean. I was at first unsure i had the correct wire, now I'm positive, stripped each wire, removed the EFIE from teh cirucit, and put a voltmeter to each wire, while gunning the throttle 2 of the wires showed static voltage, 2 of them jumped by barely half a volt, and the 5th wire would move a good 2 volts each time i gunned it. Oh right, yeah its a wideband sensor. I have 2 EFIE's i have tested the same way above, the one from eagle research for the narrowband sensor, one from Magnum Tuning for the wideband sensor.

I have found that my mileage is SLIGHTLY higher overall, it seems to be much higher at slow speeds, 35-45 mph ill see 35 - 38 mpg, the moment i get on the highway it drops back to normal which at 70 i always got very close to 30. Now im seeing closer to 31 on average.

So, heres my thoughts, After thuroughly reading Mike's Tuning for Mileage post I was thinking it was the MAF sensor, i thought maybe being an 05 the ECU was a little more intelligent and is not allowing the mixture to go lean when it detects all this air coming in the intake. This theory would support my mileage gains at lower speeds. Of course I never really checked my mileage at "low speeds" in the past(prior to HHO) so i could be way off there. It does seem excessively high at low speeds though.

I then read some posts that people ran into the downstream sensor also supplying the ecu with data making the single EIFE useless. I figure this is a possibility.

One thing came to mind: has anybody tried just unplugging the 2nd sensor?? I think im going to try that tomorrow. I just thought even if it trips the CEL who cares as long as ur still in closed loop...If it works just run it until inspection time.

any thoughts on this or my setup??

I've got an 07 Honda accord that has a wideband AFR sensor in front and an O2 sensor in the rear. Already bought a wideband AFR efie from here and put it on; no difference in mileage. Then Mike, the owner here, suggested putting a second narrowband efie on the back O2 sensor; I'm waiting for it now.
I recommend:
1. confirm that you do not have an AFR wideband sensor in front (Bruce at support@fuelsaver-mpg.com can tell you for sure). If you do, your efie won't work with it, so move it to the back and get a wideband AFR efie for the front. These guys will work with you, so write and ask them at Bruce's email address. John
01-22-2009 07:12 PM
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colchiro Offline
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RE: Downstream Sensor problem?
Regarding the rear o2, so far it looks like we only need an efie there for certain Dodge and Jeep models. You have a Nissan, so you shouldn't need to do anything. Unplug it? It's there for a reason. Let's leave it for now.

I assume you have the efie installed on the 5th wire and it's working? If not you should check out "Wide Band EFIE Installation Instructions" in my Documents link. If it's properly installed, you should be able to affect your engine or throw a code when it's cranked.

Regarding the improvement only at low speed, sounds to me like you need more hho. That 1.4 LPM you quoted, did you measure it or is that what it's supposed to put out? You might also check for leaks by brushing the connections with soapy water. I'd like to see you at 2 LPM, so I you'll need all of that 1.4 LPM, nothing less.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
01-22-2009 07:21 PM
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mtnhillsman Offline
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RE: Downstream Sensor problem?
It was measured. My electrolyser is in the trunk, so i thought of leaks too(long distance the HHO has to travel), I measured it at the last point before it enters the intake manifold, and also right out of the electrolyser, both measurements filled a milk gallon (3.78 liters) 4 seconds of each other.

I did just rework the electroloyser to get it up to 1.4 from like .4, i will need some cleansing phases and will double check the concerntration of electrolyte so might get production up a bit more.

I just read your wide band efie install instructions, which reinforces that i do have the correct wire. The only thing is the wideband EFIE i purchased does have 4 wires, positive, negative, o2 sensor signal wire, and ECU. You can see the one i have below. Is it legit?? or should i just buy one from this site?? When i bought that one it was several months ago before mike had released his wideband EFIE.

http://www.sportairfilter.com/index.phtm...mek_id=684

You say my HHO production may be insufficient. What kind of mileage gains can i expect adding 1.4 lpm to a 2.5 liter engine?? Just wondering if i should consider further renovation of my unit or start on a new one.

ONe more question: how many miles should i be driving for each test of the EFIE?? I will admit i've been rather impatient trying to get this thing working for a trip on sunday. I had been adjusting the EFIE every 10 miles or so and resetting the mpg gauge.

Thanks for all your help.

Chris
(This post was last modified: 01-23-2009 08:04 AM by mtnhillsman.)
01-22-2009 09:14 PM
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mike Offline
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RE: Downstream Sensor problem?
That HHO production is plenty. 1.4 Liters/min will work fine. I've seen guys get 50% or more with less HHO than that.

Another point: You cannot use the your computer's instant MPG readings as a way to determine what mileage you're getting. As soon as you add HHO and an EFIE, you are altering the data the onboard computer uses to calculate MPG. It's data is no longer valid. You must use miles driven on the odometer vs gals of gas put in the tank. It's the only way to accurately see what effect your changes in settings are having.

Lastly that wideband efie you bought (the one in the silver tube) is actually not a wide band efie. I bought one a while back to see what they were doing. It's a well built unit, but it's a narrow band EFIE that is being advertised as a wide band efie. We have known for some time that these don't work at all on 4-wire wide bands. The only EFIE that is actually made for wide band sensors, that I know of, are the ones sell here: Wide Band EFIE.

colchiro's right about unplugging your sensor. No good comes from that. At best, you'll just have a check engine light all the time and won't know if you've got other things set to far out of range. At worst, you'll put your computer into open loop mode and your mileage will get far worse than when you started the project.

You should make sure of the type of sensor you have. You should get the correct EFIE for it. Doing a map handling is fine, but you should be getting good mileage gains with just your HHO and an EFIE. I would debug that first. Then, you can possibly add to those gains with a MAP handler.

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01-23-2009 08:38 AM
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mtnhillsman Offline
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RE: Downstream Sensor problem?
(01-23-2009 08:38 AM)mike Wrote:  That HHO production is plenty. 1.4 Liters/min will work fine. I've seen guys get 50% or more with less HHO than that.

Another point: You cannot use the your computer's instant MPG readings as a way to determine what mileage you're getting. As soon as you add HHO and an EFIE, you are altering the data the onboard computer uses to calculate MPG. It's data is no longer valid. You must use miles driven on the odometer vs gals of gas put in the tank. It's the only way to accurately see what effect your changes in settings are having.

Lastly that wideband efie you bought (the one in the silver tube) is actually not a wide band efie. I bought one a while back to see what they were doing. It's a well built unit, but it's a narrow band EFIE that is being advertised as a wide band efie. We have known for some time that these don't work at all on 4-wire wide bands. The only EFIE that is actually made for wide band sensors, that I know of, are the ones sell here: Wide Band EFIE.

colchiro's right about unplugging your sensor. No good comes from that. At best, you'll just have a check engine light all the time and won't know if you've got other things set to far out of range. At worst, you'll put your computer into open loop mode and your mileage will get far worse than when you started the project.

You should make sure of the type of sensor you have. You should get the correct EFIE for it. Doing a map handling is fine, but you should be getting good mileage gains with just your HHO and an EFIE. I would debug that first. Then, you can possibly add to those gains with a MAP handler.

Thanks. Good info. I just ordered that wideband EFIE you mentioned. Hopefully that will work.

To throw another wrench into this... Yesterday after hooking up the so called wideband EFIE (the one in the silver tube), my CEL came on immediately after starting the car. Over the last month it has come on here and there while testing/adjusting the 2 EFIE's, always remedied by disconnecting the batt terminal for a while and restarting. I even took a 2 month break from this project and had no CEL for 2k miles. So, this time, i disconnect the terminal, start the car, bam, CEL immediately. I then remove the EFIE from teh circuit, turn off the HHO, disconnect the battery terminal again and restart. Still CEL immediately. I then remove the o2 sensor, cut all my disconnects off and solder the wires together to ensure there was no loose connections. Again, immediate CEL. I go to autozone to have them plug in and read me off the codes:

P1148 Closed Loop Control (Bank 1)

P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)

P1065 ECM Power supply circuit

P1031 A/F SENSOR 1 HEATER

One thing, although i mentioned the possibility of unpluggin the 2nd o2 sensor, i never did it, so find it odd the sensor 2 is acting up. It seems the first and last codes above should clear themselves after some normal driving. the 3rd(1065) has me puzzled, this is what alldatadiy shows regarding that code:

Trouble diagnosis name: ECM power supply circuit

DTC detecting condition: ECM back-up RAM system does not function properly.

Possible Cause: Harness or connectors [ECM power supply (back-up) circuit is open or shorted.] ECM

My assumption is that since I've been trying 2 different (wrong)EFIE's, turning the HHO on and off, constantly pulling the battery terminal everything has gone to hell. I'd have to assume after some drive time and the ECU gets some reliable data things should return to normal.

Here's the only other thing: before testing the "long silver tube" EFIE i tried wrapping the first o2 sensor in aluminum tape. I had a CEL within 5 mins. I immediately removed the o2 sensor but the aluminum tape was gone, fell inside the manifold. Based on the layout it would just fall down and go into the CAT. I pulled the battery terminal, started the car and had no CEL for 100 or so miles. About 2 square inches of tape is inside the manifold, i was thinking the glue burning off the one side might trip the 2nd sensor, being there primarily for emmissions.

feel free to call me an idiot.... Crazy I'm taking the car to key west on sunday, and was hoping to get the mileage up by then, guess thats not gonna happen. I figure ill take the car anyway since my mileage is still good (doesent appear to be running full rich). Hopefully that long run will reset everything, no HHO, no EFIE.

If anybody has any recommendations id surely appreciate it, i have 6 mos till inspection time so not too worried. It woudlnt take much for me to throw in a new 02 sensor and put on a new intake and take it to a dealer(so they dont see my mods) since its still under warranty.
01-23-2009 01:07 PM
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colchiro Offline
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RE: Downstream Sensor problem?
Thanks Mike. I was going to comment on the computer mpg vs mpg the old fashioned way, but forgot it with all the changes I made to my response.

I agree with Mike, AFAIK, he has the only wide band efie. That doesn't mean other aren't in the works.

I was under the impression that the aluminum foil goes on the outside of the sensor and the wiring. Bear in mind that anything that burns or melts in the vicinity of an o2 could ruin it.

You have what appears to be two heater codes on 2 different sensors. Did you blow a fuse? Unless you cut or altered a heater wire, I see no reason to have heater codes.

At this point, I'd regroup and see what codes clear up and go away when you use no efies and no hho. If you can go for a few weeks without problems, I'd slowly introduce things one at a time, starting with hho.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
01-23-2009 04:38 PM
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mtnhillsman Offline
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RE: Downstream Sensor problem?
(01-23-2009 04:38 PM)colchiro Wrote:  Thanks Mike. I was going to comment on the computer mpg vs mpg the old fashioned way, but forgot it with all the changes I made to my response.

I agree with Mike, AFAIK, he has the only wide band efie. That doesn't mean other aren't in the works.

I was under the impression that the aluminum foil goes on the outside of the sensor and the wiring. Bear in mind that anything that burns or melts in the vicinity of an o2 could ruin it.

You have what appears to be two heater codes on 2 different sensors. Did you blow a fuse? Unless you cut or altered a heater wire, I see no reason to have heater codes.

At this point, I'd regroup and see what codes clear up and go away when you use no efies and no hho. If you can go for a few weeks without problems, I'd slowly introduce things one at a time, starting with hho.

I did cut all wires on the upstream sensor, had to get a socket on it to get it out. I re-attached all wires with disconnects and tested for about a day without the CEL coming on. It came on only after hooking up the 2nd EFIE. Now everythign is soldered returned to factory. I'll check the fuses, good idea.

So your saying i may have ruined the upstream sensor as teh one sided foil tape burned off?? How about the downstream sensor and the CAT?? would you think that foil rolling around in there would cause any harm ??
(This post was last modified: 01-24-2009 06:47 AM by mtnhillsman.)
01-24-2009 06:43 AM
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colchiro Offline
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Post: #9
RE: Downstream Sensor problem?
I suspect the foil on your sensor blew off and is in the muffler, or more likely, on the ground somewhere. I doubt it would hurt the cat. As a precaution, I'd just drive it like this for a week or two to make sure you have a stable setup. Once you know this is good you can proceed again, changing just one thing at a time.

OTOH, if you still have issues related to the rear o2, I'd do a visual on it and see if there's residue.

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
(This post was last modified: 01-24-2009 07:46 AM by colchiro.)
01-24-2009 07:46 AM
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saltmine Offline
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RE: Downstream Sensor problem?
Guys, the "downstream sensor" is there purely to monitor the performance of the catalytic converter,,,period.

It does this by comparing the voltage reading of the upstream sensor with the output of the downstream sensor. All things being equal, the downstream sensor should read quite a bit less than the upstream....which tells the ECU that the catalyst is working properly.

I think the problem most people are running into is the upstream sensor voltage gets too low, and the differential between the two isn't enough to satisfy the ECU.

ALL computer control systems since 1979 use the oxygen sensor for fine tuning the fuel trim...
01-24-2009 09:39 AM
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