'85 911 RoW Oxygen Sensor/DME Question
 

About a year ago I picked up an '85 911 RoW. It's been great. Today I was doing a little work and I noticed an extra white box with four leads (brown, yellow, orange and red) running into the DME and one white one that went under the carpet somewhere else. It says "Fuel Control Unit for Porsche Carrera" and has an address for "DC Johnson and Associates" in Laguna Hills, CA. It was poorly ziptied in place and was clearly an aftermarket addition. I have also noticed that the O2 Sensor has a white wire so I'm assuming this little box was part of the federalizing of the gray market car. I'm wondering what it does and if I can remove it? I'd like to "de-federalize" the car as much as possible (obviously without removing things like the door braces). I was planning on getting a pre-muffler as well to replace the cat. Thanks in advance.

Tripp

Here's a pic of the box underneath the seat.
http://forums.pelicanparts.com/uploa...1127679101.jpg

bump

I have an 85 RoW as well. There are a bunch of threads out there on hesitation issues, surging, etc. In those threads, you will see a photo of that same unit. Speculation at that point, if I remember correctly, was that it served no purpose.

I ended up unplugging my o2 sensor due to some surging issues I had. I did a bunch of troubleshooting, etc and was unable to resolve the issue. Unplugged it to see what would happen and my problem was gone. The sensor was making the car run too lean in the mid rpm range.

Also, take a look immediately in front of the front oil cooler in front of the passenger front tire. See if there is a canister there. I pulled mine and it seemed to have no purpose. It was some type of purolator canister/filter that had hoses running to the motor. The hoses had broken and it was serving so purpose so I pulled it. Still don't know what it's function was but I do know it was blocking airflow to the oil cooler.

http://forums.pelicanparts.com/porsche-911-technical-forum/219748-what.html

Good luck and enjoy the car. They are a blast.

How about taking the seat off and taking a picture of the DME and how this puppy is hooked into it. I have a US 85 model and have never seen anything like that on it or the others I have seen.

JoeA

Thanks for the info.

I can say that the wires from the unit run into the fat cable that plugs into the DME so I'll need to try and figure out which pins on the DME plug interface are connected to its wires. I'm doing the valves this weekend so maybe I'll pull the whole DME and see what's going on in there and what those wires connet to. I've heard that sometimes the federalizing agencies would add electrical components to alter the function of the circuitry (shudder...). I'll let ya know.

"Today I was doing a little work and I noticed an extra white box with four leads (brown, yellow, orange and red) running into the DME and one white one that went under the carpet somewhere else."

It's a Mickey Mouse box used when the Euro cars were imported into the US
to allow for a O2 sensor hookup which the Euro cars lacked in the DMEs.
It modifies the AFM input based on the O2 voltage.

That's what I figured it was. Can I just unplug it and throw it directly in the garbage or does the DME need some "fixing" as well?

I recall a year or so ago, someone else posted pics of an aftermarket box similar to yours. As I recall it was used to work with an 02 sensor which the ROW Carrera did not have.

Loren, What happens here? Do they have to run a wiring harness from the DME to the O2 sensor when this mod is made or does the plug-in exist on all the 911 harness's and is not used on the ROW cars?

JoeA

If the box is removed:

1. The AFM must be connectd properly to the DME unit.
2. The O2 sensor function will not work if a Euro box is used but the DME unit
lacks O2.
3. The pin 24 on the Euro harness for the O2 is non-existent.

Thanks for all the info. I'll try unplugging it and hooking up the AFM correctly. I'll let you know what happens. I occassionally get mid-RPM surges in 2nd/3rd gear when not accelerating so maybe it's just the old O2 sensor.

Loren,

Would a US DME wiring harness attached to a Row DME 0261200051 function with the o2 sensor. And are there any other mods required.

Thanks

Ron

"Would a US DME wiring harness attached to a Row DME 0261200051 function with the o2 sensor. And are there any other mods required?"

No, the 051 DME unit doesn't have the O2 circuitry and EPROM.

Thanks my friend

Ron

So, several months later now, I have needed to get emissions done on the Porsche and it failed. It failed on the HC level by a couple hundred points and last year it just barely passed by 50 points. So it was time to figure out what the hell was going on and we know this magic box is too blame (well, probably). Please bare with me.

The magic box is sewn into the wiring harness by six wires. The six wires it has are orange, yellow, white with shield (so that's two pins), brown, and red. Brown is ground to the box, red is power to the box, the white wire goes to the O2 sensor on the cat and is shielded so is effectively two wires. Then the orange and yellow wires are spliced into a single black/red wire in the harness. The black/red wire goes to pin ?? (I don't remember I fill in the number later) on the DME (I have a Euro DME - 051). This black/red wire is for the NTS II (negative temperature sender - it's basically a variable resistor, the warmer it gets, the lower the resistance), the main temperature sensor for the engine located on cylinder head 3. Basically what is happening (and what is really, really bogus) is that the magic box is taking the reading from the temp sender and changing it depending on the O2 voltage. This differs from what loren said. My setup does not modify the AFM circuit with the magic box, just the NTS II reading. The idea of the NTS II in the DME is to basically increase the pulse width of the injectors as the engine heats up which makes sense - more gas when the engine is warmer. The DME adds "more gas" by increasing the duration of the pulse width to the injector. What the federalizers did is lean out the engine with the adjusters on the AFM and then use the magic box to modify the NTS signal (i.e. increase the injector's pulse width) therefore providing more gas when the reading on the O2 sensor was too their liking. It's fooling the DME into thinking it's running cooler than it really is and it's running lean! The lean running is precisely the reason for the high HC content in my emissions test.

It turns out the my O2 sensor was bad so that means the bogus magic box was never richening the mixture so it was always running lean! Anyway we've replaced that with a used O2 sensor for a VW golf that was lying around and slightly adjusted the AFM to make the car run less lean. It will be back at emissions this week and I'll let you know the results.

In the immediate future I'll be removing the cat and replacing it with a bypass and removing the magic box and just jumping the NTS-II wire back together (that's all you have to do to remove the box, we tested it). I also have to mess with the AFM, as both the lean screw has been adjusted and the knob or whatever it is inside the AFM (I haven't opened it up yet, but the large cover was glued on so that means it's been messed with before). Hopefully I can then go back to the old setup whenever I need to do emissions which will only be for three more years anyway in CT.

you mean "bear with me"....right.....

no way I'm gonna "bare" with ya buddy........

Wil :)

Found this old thread about an issue I'm dealing with - here is what I have under the seat on my '85 RoW
I have one wire going into my "Mickey Mouse" box - the white wire that comes from my O2 sensor.
There are 4 wires coming out. Then, at the harness, 2 of those wires have been cut.
How do I go about taking this whole setup out of the system?

http://forums.pelicanparts.com/uploa...1235101561.jpg
http://forums.pelicanparts.com/uploa...1235101577.jpg

Disconnect it and see what happens. I would suggest putting it on an analyzer to check the fuel mix, before driving it much....

Ah, someone else has the same piece of sh**!

Red is power to the unit, brown is ground, white is the O2 sensor. You can cut those those three and ignore them (but cap off the red wire so it doesn't short out anywhere). Orange and yellow should be connected to each other to get the wiring back to the way it's supposed to be.

If you cut away the electric tape on the harness you will see that a red/black wire has been cut and on one end is attached the yellow and the other end is attached the orange. This is so the unit can modify the signal on red/black wire (NTS II - head temperature sender). Does your car seem to be running lean? I would imagine this is the case seeing at your NTS II wire is not hooked up at all in the current configuration!

Anyway, connecting those wires will get things mostly back to normal, but you're not done yet. If you have ever taken apart your AFM you will notice it has been tampered with (by the federalizers). You will need to take the car somewhere with a quality gas analyzer and have the AFM re-tuned.

I haven't done this yet because it's expensive and I still get occasional "bucking" at around 2800rpm at a constant speed in 2nd gear. Good luck.

Thanks - I was trying to get through emissions in GA - I had a friend take off the bypass and mput on a cat that was with the car. That's when my problems started.
My first emissions test without the cat was by far the best that I had, even after adding a cat.
I have finally figured out that the O2 sensor must be bad as I have been having warm start issues and a couple times have stalled when at idle - it would then take about 30 minutes for the car to col down before it will start again.
I'm now convinced that all this mickey mouse stuff must be the problem.
I'm going to take it all off and see see what happens.
When you say it's going to take a lot of money to get the AFM back in shape, what type of quotes have you had?

Be careful with that cat! Because the orange and yellow wires are not hooked up, the box is not regulating the NTS II like it's supposed to, it's possible that you could burn up a perfectly good one if that box isn't working correctly.

I assume you were failing for high HC? That's what I was failing for and the cat won't help. You are failing on HC because the combustion temperature is too high due to the mickey mouse box messing around with the NTS II signal (or, in your case, not have an NTS II signal at all).

These grey market cars, as you've found out, should not have a cat and should not have the mickey mouse box. I have heard that if the box and the cat is removed and the AFM is re-tuned to original, then it should pass emissions just fine (depending on the state's limits).

I think tuning the AFM is only a couple hundred, but you'll want to find a porsche specialist who knows what they're doing to do it. A dealer probably wouldn't even know what to do. My car is in CT (I'm currently in CO) and I was busy getting ready to move out here so never got around to it. I think I will this spring.

So, your steps should be 1) disconnect the mickey mouse box, 2) connect the orange and yellow wires to each other (thereby reconnecting your NTS II signal to the DME as it should be), 3) have your AFM tuned by a porsche/race specialist with an exhaust gas analyzer, and 4) bring it back to emissions.

Then report back here with your emissions results.

I'm going to get into the box when I get back into town next week.
I want to get the AFM back the way it was before the boat ride.
I now have the bypass back on the car and need to get a plug for the O2 port.
I'm really surprised at how well the car ran with the cat hooked up and those other wires cut. Glad I didn't take any long rides and fry the unit.
I found a way around emissions - next year I won't have to worry about it when the hits the magic 25.

Thanks for all your help and starting this thread 4 years ago.

No problem. Let us know what happens with the AFM. I found a way around emissions as well and by the next time I register I will have hit the magic 25...

What is the process for tuning the AFM?
Is it simply getting the CO% within a range?
What is the range I should shoot for?

When at an emissions station - in our state , if you find the right guy, we can set up the machine for diagnosis mode, this will tell you what all the gas readings are. Should we be able to adjust the AFM using a 3mm hex to get the readings thus resetting the AFM?

This same guy also promises I will pass the test - I didn't ask how but am glad I finally found THE guy.

The first thing to do is to see if the spring setting has been adjusted on the AFM. This should be obvious as the black plastic cover for the spring will look like it's been pulled off and then glued back on. Hopefully the federalizers marked the original location. After that, you need to have the car warmed up and running with the exhaust gas analyzer inserted in the tail pipe. You then adjust the AFM with a long allen key to get the correct CO numbers.

I haven't messed with it in a while and I don't remember the numbers. I'm sure they're on this forum somewhere and they're also in the Chilton manual. The exact procedure is probably here somewhere as well if you search for "AFM adjust" or something like that.

Forgot to mention. There is alot of AFM info here from Sal Carceller:
http://members.cox.net/widebody/AFM/AFM3.2LCalibration.doc

I just came across this thread. I am in the middle - actually towards the end of my engine rebuild - of converting all the electrical wiring back to stock/normal. Long story short I have an original German 3.2 1984 Carrera. I bought it from another German who had imported it and obviously it was undergoing the "let's f*** up this car the best we can" procedure. Today I just removed this woodoo box and tomorrow I will get some 21 ga wire and the connector pin for the DME wire connector to hook up my 3-wire oxygen sensor. I noticed several folks have posted the intention to convert their ROW cars and I am wondering about results and tips - if any.
Anyways my thread is here:
http://forums.pelicanparts.com/911-engine-rebuilding-forum/545476-911-3-2-3-4-conversion-engine-not-running-2.html#post5402680
...and it shall continue until it's done :D

Wanted to close this one off after quite some time. I finally put together a WBO2 2Y2 kit (WBo2 2Y DIY Wideband Unit) with a buddy and used a Bosch LSU 4.2 wideband O2 sensor to analyze the exhaust gas. I ended up moving the AFM spring cog 6 clicks counter clockwise (richer). I never could tell where the original setting was. Moving the spring cog eliminated the surging I was having at light-partial throttle (constant 2300-2800 rpm), but made the idle too rich and it surged on startup idle. I adjusted the AFM idle screw out about 7 turns from all the way in to lean out the idle, but it's still a bit rich. Whatever, these cars weren't mean to idle...

Anyway, at long last, success! In short the steps to de-federalize your RoW 911 Carrera were removing the federalizing box, reconnecting the DME wires back to stock (it's just one wire that needs to be spliced back to itself - see above), replacing the cat with a bypass/test pipe (a bypass pipe with an O2 bung is key for installing your wideband O2 sensor for testing), and adjusting the AFM spring cog and idle screw to get as close to stoich as you can during load and idle.

This will probably not pass emissions in states that just test idle (maybe with states that dyno), but you can always readjust the AFM spring cog to lean the thing way out just for emissions. It'll run like crap, but I've heard you might be able to get it to pass.

Having some sort of exhaust gas analyzer is the trick, and the WBO2 is definitely the cheapest option ($100 without the O2 sensor itself). You'll need some computer hacking skills to get things up and running, but it works well once you figure it out.

Please do not close this , There are still people out there that have questions and you or someone else might help. Like me I have a question, I have an 85 euro and the box I have looks a little different so some advice is needed. My car runs rich all the time ( I can smell the gas ) The box I have has blue , purple, yellow, red , brownand I think black wires. I would like to take this off any suggestions on what to do with this style.
http://forums.pelicanparts.com/uploa...1419944207.jpg

http://forums.pelicanparts.com/uploa...1419944242.jpg

A quick google search shows that unit to be adjustable. There is a .pdf file on Rennlist that explains the Neutronics unit:

https://www.google.com/#q=neutronics+lambda+computer

Thanks kidrock, I would like to remove it if I could. I do not have a CAT but do have an o2 sensor. What are the advantages of removing this from the system

Well, I didn't go too far into what that box actually is...but if I understand correctly, those boxes were installed to assist in tuning in fuel/air mixture ratios in order to pass stringent smog regulations.

I believe that some of the links showed how the unit is tapped/wired into the DME. If you remove the seat and take the time to see where it has been piggybacked into the DME, it should be pretty self-explanatory.

I would disconnect the battery for sure. I would also do an extra-good job on the wires...the DME is basically the car's "brain", and shoddy work down there can be problematic in the future.

I would also be concerned about what the actual fuel/air ratio will be after the unit is removed. There are many threads here about the use of LM-2 air/fuel ratio meters, or you can have it checked out by a local independent shop.