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Yesterday I decided to see if my AFC really does it's thing leaning and richen things up.

OK here is what I have that is relevant to what I am talking about.

- AFC well duh :)
- Autometer A/F
- stock injectors (yes still NA and would rather stay NA)
- I happen to be one of the few guys who got CEL right after installing the AFC, I keep getting code 14 which has to do with the Map sensor voltage, so far I have talked to 2 people who got the same problem as me and they all also have 96 "umm I wonder if that has anything to do with the CEL"

anyway 3 weeks ago I decided to do the blue wire mod to my AFC (Autometer A/F gauge looks nice while it flashes and all, but trust me, it would do you anygood tuning wise) and as soon as I did the blue wire mod, my Autometer A/F started bouncing a lot slower than b4 the mod, and in the morning the car A/F gauge would start bouncing after 5 mins or so, b4 the blue wire it would start bouncing after 30 seconds of starting her up at the most.

I started with having all of the AFC settings at "0", went WOT in 3rd gear while I was looking at my AFC to find out that my O2 voltage was between 0.87 - 0.89 looking at those numbers I thought my car was running abit lean, so I went ahead and richen things up by 10% across the board, took it again to WOT in 3rd gear and got the exact same readings "WTF" went crazy and went all the way to +45% and got the same readings (my EGT probe gave up on me a month ago so that's why I could not even tell if the car was running lean or rich, all what I was working with was the AFC readings after the blue wire mod)

So for the past 2 weeks I was running without AFC cause I thought it was not doing its thing especially after reading on the manual that once you get the code I am getting, the ECU ignores the map output and uses the TPS, speed, and the other sensors to determine the A/F mixture.

Yesterday I got hella bored so I decided to see why I keep getting the map voltage code all the time, I still did not find out why, I guess it's got to do with being one of the earlier OBDII cars (anyone has a 96 NT with the AFC installed and CEL?)

since I was not able to fix the CEL problem, I went ahead and hooked my DVM to the A/F wire, now however my led A/F gauge bounces a lot slower, so I thought maybe I am drawing too much current voltage or whatever from the O2 sensor and that's why as soon as I did my blue wire thing, the A/F gauge was bouncing slower, so now I disconnected the blue wire mod and only used my DVM.

so now I decided to run my car again to WOT in 3rd gear and had all my AFC settings at "0", and guess what? my DVM was showing 0.95 volts all the way till 5500 rpm and would jump to 0.98 volts till I hit the rev limiter (I guess the dealer wanted to play it safe and just made the car dumb even more fuel at higher RPMs)

So now I know my car was not running lean as I thought after looking at the AFC readings using the blue wire mod. So I went ahead and leaned things down by 5%, the voltage drooped to 0.94 and would jump to 0.96, so now I know my AFC actually does what's supposed to do. I leaned things even more (8% this time) and now I have my O2 voltage at 0.92 , but I would rather keep it there for now till I get new EGT probe and go from there.

Lesson learned
The blue mod is not as good as we all thought, if it caused my A/F gauge to bounce slower than b4, so it's either interfering with the actually O2 voltage which is no good, or maybe using 2 O2 sensor gauges at once draws too much current or voltage from your O2 and causes you to see less voltage than it actually is.

Adel

That's some goo dinfo for the future. (I'm sure I'll have an S-AFC eventually) I'm going to go with the two guages causing the problem. If you have some free time you can disconnect your A/F guage and just do the blue wire mod. I'll bet your results will be the same as when you disconnected the blue wire. I'll bet the draw on current was just too high for the ECU to read it properly. This may not be a problem with later ODBII systems, they may have reprogrammed the ECU or wired thing diffrently which is why it seems only 96 model year is effected.

I think a good test would be to unhook both A/F and blue wire and then read your voltage with these settinga and see if your readings are the same. Just an idea for a rainy day.

"To strive to seek to find... and not to yield."
Michael J. Kulaga
Michael_97RS@2gntDSM.zzn.com
aol IM: MJKulga
http://highlander.dsmpower.com/

Hey adel,

Good job! Now you can install my S-AFC! lol j/k

Does the car feel faster?



"RACECAR backwards is RACECAR!"

Kory
korynguyen@yahoo.com
Happy Honda Hunting!

I agree, it's probably because you've got two things hooked up to it at the same time.

I also have a CEL with the SAFC. I don't know what the light is for but I'd guess the safc is causing it. I can't be sure because I had the safc on for a while and there was no cel light, and the light came on after I adjusted it slightly lean, but not immediately after I adjusted it!

go figure, damn if I know why it would wait before giving me a cel, maybe I didn't get the connections as good as I thought.

Todd Scungio
98 RS
15.803 @ 86.48 MPH

You are correct about the whole added resistance thing to your O2 sensor readings. But honestly I believe that its your Autometer A/F gauge that is the problem and not the "Blue wire mod".
Personally I would not use either. The blue wire mod has been known to do some freaky stuff (it's on there for Nissan 300ZX sensors or something like that). What some of us were wondering was if the AFC sends a signal back through the "blue wire" or even if it modifies the signal...

BTW My A/F gauge (Jumptronix Digital) cyles as soon as I turn the car on...

P.S. Making a "cheap" device to lean your car out all across the board is actually very simple.. All you need is a suitable resistor placed in the correct location ;-)

Guy
RS_Guy



I might actually be *driving* my car soon!
Its only been 6 LONG months...

Damn the waiting..... It Sucks!

>Personally I would not use either.
>The blue wire mod has
>been known to do some
>freaky stuff (it's on there
>for Nissan 300ZX sensors or
>something like that). What some
>of us were wondering was
>if the AFC sends a
>signal back through the "blue
>wire" or even if it
>modifies the signal...

Maybe that's why some people are getting check engine lights with the SAFC. It could be messing with the O2 volts and the computer can't figure out what's going on.

Todd Scungio
98 RS
15.803 @ 86.48 MPH

>
>P.S. Making a "cheap" device to lean your car out all across the board is actually very simple.. All you need is a suitable resistor placed in the correct location ;-)






And would you be the one that would know what this resistor is and where it goes?

I don't think the blue wire (input 2) puts out any voltage, so it shouldn't mess things up that way. I would have to agree that you have proven that too little resistance to the o2 sensor signal wire reduces accuracy, but I would just keep it to 1 metering device per sensor (i.e. either an air/fuel gauge/ voltmeter/ or super afc). The afc should give the same results as the voltmeter in the same situation, but don't use both at once. there is no need. also, the air/fuel gauge is worthless compaired to a true digital read-out (acutal numbers). might as well sell it and just use the s-afc's sensor check function. The blue wire mod works great on my Stealth, and I also use input one for my knock sensor. 420A's can't do that because they use pressure sensors instead of karman vortex MAF sensors, and the readings I have obtained by using my s-afc this way has proven to be beneficial. The inputs that aren't normally used in tuning your vehicle (input 2 in this case) don't have any affect in the functions or adjustments made to your air flow readings.

Bring it on............

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Armond30, that makes a lot of sense, but howcome when I had my Digital Volt meter
along with my Auto meter A/F gauge the readings seemed to be fine and the LED A/F gauge was bouncing normally, but when I put the AFC along with the LED meter, things start to act funny ! !

using the led A/F gauge with the DVM seemed to give me the right readings.

Using the led A/F gauge along with AFC blue wire seemed to mess things up.

The only thing that I could think of is that the AFC draws more current than the DVM, but again both of them use independent power wire or power source ! !

not trying to prove anyone wrong here, I am just curious.


Adel

I wonder how both actually measure the voltage.

If you get a GOOD Voltmeter with options there are many ways to measure voltage some drawing various levels of current and some not... I wonder which is used in each case. I also wonder what is within acceptable limits of the ECU to process the signal correctly...

No Actual Knowledge In This Post!

"To strive to seek to find... and not to yield."
Michael J. Kulaga
Michael_97RS@2gntDSM.zzn.com
aol IM: MJKulga
http://highlander.dsmpower.com/

not exactly sure on that one. you don't have anything hooked up to output-2 do you? I forget which wire that is, but it is the one you would normally use with the blue wire to hook the afc up to a second maf sensor. also, was the check engine light on when you tested it with the afc? usu. when the ecu goes into limp mode, it tends to mix slower.

Bring it on............

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I have always had the CEL after the AFC was installed. the car drives fine tho, I still could not find out why my ECU does not like the AFC.

Adel

Apparently, this blue wire mod is a known problem as its impedance differences with the ECU effects closed loop operation.

Here is a post regarding it:

"for all of you using this to monitor O2 sensor voltages you will
prolly notice the car runs odd.
The afc's blue wire impeadance is to low to be used with the o2
sensor unless you dont mind it afecting the voltage by droping it .1-
.15 volts, and when the ecu see's this lower voltage it will add more
fuel to try and bring it back up. which wont happen.
my advice is to unhook this wire from your o2 sensor and either get a
a/f guage or a modified one or something like the jumptronix or the
ones gadgetseller has.
i know this from personal testing with some rather highend
electronics equipment on my personal and other peoples cars .. not
only dsm's "

Electrical egnineer's solution:

"If he's right, and the S-AFC has a low input impedance which is
dropping the O2 sensor voltage, you can fix this with a simple
circuit.. All you need is a op-amp follower - this will have a
very high input impedance (10 meg ohms) so it won't affect your
O2 line going to the ecu, and a low output impedance so it will
drive the S-AFC with the correct voltage.. All you need is a
tiny radio shack PC board and a TL082 op amp or something
similar. The wiring is very straighforward - no extra components
are needed."

Either way, it's a good thing we all know and understand the related problems.

On another note, Corbin has just sent me his Digital A/F meter. I hope to get it in soon and post my review along with pictures. :-) (it already is a great looking piece!)

Jason
98' Eagle Talon ESi-T
Mitsu Super 16g Turbo(HRC)/Custom FMIC


http://springfielddsm.homestead.com/JasonsPics.html