I really hate to say this, but you may need to either find a simpler solution or someone with the expertise to sort out your setup. I know you've been struggling with this and I get the sense that you're are pretty close, but just far enough off to make it really frustrating for you.

Maybe you could pay for someone skilled like Hobieboy or Mike Bonkalski to come sort it out for you on site.

Lets eliminate some questionable things..

First check your WB output.. pull the sensor, and measure the voltage on the white wire.

In free air that wire should have 5 volts. Now take a butane lighter and spray the end of the o2 sensor with butane
(don't light the lighter, just trigger it so butane is released). You should see the voltage in the white wire drop to 0 or near 0 when exposed to butane.

If your WB sensor reacts as above you sensor is working correctly

Note the graph PLX provides regarding the 0-5v output

http://www.plxdevices.com/M-Series-Controllers/WidebandOutputGraph.jpg

Also Ive built a few dozen+ EFI equiped cars, and we have never had to shield the TPS wiring. I also have no idea what capacitor your using with the PLX, Id revert to KISS theory here.

Your saying you see a change in voltage of only 1/2v between idle and 2500 rpm... this is a good thing, as you always try to tune from rich toward lean.. If your reading 1/2v at 2500 that means you are running around 11:1 AF at that point.. ok now lean out the load cells at 2500 what happens?

I dont know if the MS software shows you where on the VE table the engine is operating, but raise the rpms to 200 or 2500.. and adjust in real time the fuel in the cell where the engine is operating. You can even adjust surrounding cells

mppickett I would gladly pay someone to solve my issues but so far I can't find anyone willing. TimT I will try your suggestions on checking the O2 sensor.

Do you mean that the filter (capacitor) is installed in-line with the ground wire? If it is really a capacitor, that will not work, as it will prevent the O2 controller from getting proper power. I will skip the electrical engineering theory behind this, but in short, it could explain your strange output voltages.

I would remove the capacitor completely and see what happens to your signal. Easy enough to put it back if it turns out you do have a noise problem - but you need to get the output voltages in the right range first, and worry about the noise later.

Good luck,
Scott

Richard,
Lots of good advice here... so yes, sort out the O2 sensor reading first.
Star-wired ground simply means make sure all your sensors are grounded directly thru the MS and the MS is grounded to a single point (engine block is ok).
I think you are close, so keep at it. Good luck...

I will eliminate that capacitor this weekend and hopefully that will improve my O2 sensor reading.

Start with the basics as others have said. If the car will idle, adjust the idle mixture to see if the O2 sensor will respond. Don't worry about blipping the throttle and trying to adjust the map elsewhere.

If the O2 is reading 0 volts, perhaps you really are 10:1 AFR. If that's the case, pull the plugs and they should be black. Just keep leaning out the idle to see if the O2 sensor responds. Eventually you'll be lean enough that the engine will stop running. You can't do any damage by trying this.

update- we're getting closer
 

Today I removed the noise filter/capacitor and my O2 sensor seems to be working correctly ! At this point in time I don't want to jinx anything but I think it's now a matter of tuning. I adjusted the VE table once the engine was off cold enrichment and I was able to get my idle AFR to move from 10.5-1 to 12-1 so the gauge in megatune is showing movement where it wasn't before. I have asked a local to me MS guru ( Jim ) to give me a hand for one day to hopefully get this done. I will post my progress as I tune but hopefully the worst is behind me. I've said it before but I can't emphasize enough how much I appreciate all the help this board has provided. Great group of guys!:) SmileWavy

Cool. NOw get those AFRs near Stoich with no load and then start tuning on the road.

Re: update- we're getting closer
 

Woohoo! Great news:)

Congrats Richard...

Sounds like you are finally getting to the fun part :)
Just be patient with tuning! With a reliable wide band, you can tune a LOT before having to hit the dyno for the very last bit.

Great thread, and very pertinent to my situation, as I am debating switching to EFI on my 72 E (now running Webers on its 2.7 conversion engine). I would love to have the reliability and better fuel economy that should come with a well-tuned and -selected system, and to put the Webers in careful storage until I can trade them for a small island or something...

Given my research to the contrary, I am trying to think of a single, SPECIFIC and QUANTIFIABLE technical reason why the above-quoted statement would be true. Does anyone have a link to a controlled study where carbs made more than EFI on the same engine, and more importantly, why? I understand the usual arguments for carbs (atomization, cooling the intake with fuel, etc) but I think they have all been effectively debunked.

In short, I agree with the hackneyed "LP vs CD" analogy for the carb vs EFI argument. EFI is better, just not as cool...Help me believe otherwise, IF you have data.

Re: update- we're getting closer
 

Noise capacitive filters/suppressors should be wired in parallel to the device never in series. In other words, one lead would tie to ground and the other lead ties to the signal output of the O2 sensor. Inductive(coil) noise suppressors wired in series.

Did the O2 manufacturer recommend the filter?

WE HAVE SUCCESS!!!!! Yesterday " Jim-MS-Guru" came over to my house from Crystal River Florida about 2 hours away. We started around 10:00 in the morning and finished around 2:00 AM ! I NEVER would have been able to get this running without his help, man did I learn a lot. First thing we determined was that my O2 controller was not working correctly/at all. We ended up pulling it out and went to a local speed shop and they verified that the controller was no good, $425.00 later ( yes I got ripped ) we had a new Innovate LC1 with digital readout gauge in hand. We installed that and then tried to proceed but ran into additional roadblocks. During the analysis of those roadblocks we discovered that parts of the MS relay board were dead so it appears ( as I suspected about a year ago ) that the relay board is a piece of crap. We were able to "hot wire" around the dead zones but it cost a lot of time troubleshooting and then repairing. Now on to the tuning. I would say we spent about 4-5 hours actually tuning on the road. Once again without a 2nd set of hands you can't do this by yourself. Jim worked the keys on the laptop like a seasoned veteran and tried to talk me thru everything he was doing so I would understand. I have a fair amount of "cleanup" work to do on the wiring as I have jumper wires all over the place and ground wires to tidy up. Now how does the car run? I have amazing throttle response!!!! I mean immediate to the point that if you don't hold your foot steady on the pedal she reacts to minute movement of the throttle pedal. I may have to add some friction to the linkage it reacts so quickly. She pulls like a freight train up to 7000 rpm I couldn't be happier. I must have started the car 500 times yesterday and she starts right up. She is running on 6 squirts per cycle with a interesting VE table it kind of looks like a giant wave you could surf on this VE table. And the AFR gauge in Megatune matches exactly the Innovate gauge we mounted temporarily on the wiper stalk. I am cruising/light load around 13.5-1 and when I tromp on it we are staying around 12.5-1 thruout the rpm range. Sorry for the long post but I just am so happy she's running good that I wanted to share. Jim said it was a learning experience for him also as he hasn't done a 911 with ITB's before. And yes I payed him, he was a pleasure to meet and work with. O.K. enough typing it's time to drive. Thanks guys.,

Great news!
-Chris

Great news. Could we get the guys running Tony's EFI or Mega Squirt to show the final tune to help out the rest us?

That is truly fantastic news. I was planning on going EFI on my 3.4, got very worried about the ability to tune it acceptably when I read your thread.

Real encouragement for us lurkers....really appreciate you sharing your experiences and the help on this list is awesome!

Dennis

Unfortunately the joy of EFI lasted about 6 hours, went to start it this morning and she runs like crap. It's as if Megasquirt has lost data from last night???!!! I believe I am done with this project and will be turning the car over to my mechanic. He will either install a different ECU or we'll go with PMO/Webers as I am mentally fried on this. I really thought we had it last night but apparently not. Good luck to anyone contemplating this in the future. You may see my items in the classifieds. I think I'll drink heavy today.

Not encouraging news for the rest of us in the process of MS EFI conversion. Sounds like you at least got a taste of sweet success yesterday. I would think that going with an ECU supported by one of your local tuners would be your best bet given the investment you have already made. Good luck!

Is there anyway you can ditch this "hot wired' MS II? If I lived anywhere near you I would loan you mine right away. It really sounds like it's just bad. I have never lost the config on mine.