Installed in PLX Wideband O2 in my '83 SC

[tirwin]

Thought I would document my install of the PLX wideband O2 sensor (and gauge).

First here is a link to the PLX page:

PLX SM-AFR | Wideband UEGO Air Fuel Sensor

And here is a picture of the unit:


Description of the interfaces:

1) 12V power input
2) 4 Prong Analog Clip
3) Termination Jumper
4) Serial RX Plug (In)
5) Serial TX Plug (Out)
6) Sensor Input Clip

Picture of the unit installed in the car. I chose to install it next to the PermaTune CDI box.



I have installed the gauge in the engine compartment temporarily, but here is what it looks like with the unit on:

[tirwin]

There's not a whole lot to this. I forgot to take pictures because I was in a bit of a hurry that day.

I went to Harbor Freight and picked up an O2 sensor socket for a 3/8" socket. Came home, jacked the car up. Removed the old O2 sensor and installed the Bosch wideband O2 sensor that came with the PLX unit. I had to take off the heat shield around the cat but that's no big deal.

As you can see, there is a big fat connector on the end of the Bosch unit. Oh, crap! I was desperately trying to figure out how to get that big fat connector through the tiny grommet the wire from the old O2 sensor went through.



Then I had what alcoholics refer to as a moment of clarity. There is a rubber flap between the engine tin and the body just above the hole the wire from the old O2 sensor used to go through. I was able to just push the new O2 sensor through that flap. Done and done.

[tirwin]

Next I had to decide where to mount the sensor module. The unit comes with a bazillion linear feet of wiring to connect the O2 sensor to the module. At first I thought about putting the sensor module in the cabin underneath the passenger seat right next to the ECU. But as I started looking through the directions more carefully I thought that might not be such a wise idea.

After drinking a beer, I said to myself, "Self, you should just put this thing next to PermaDoom. Yea, wiring in the gauge is going to be a whole 'nuther pain in the tuckus. But the problem we are trying to solve here is we need a narrowband output signal sent to the ECU and we need a ground and a source of switched power."

After another beer, I decided I was right.

Now, how are we going to mount this thing? So I says to myself again, "Are we really confident this is going to work?"

"No," says I matter-of-factly.

"Should we invest a lot of time permanently installing this thing if we don't know for sure it's gonna work?"

"No," says I.

"Do we have any of that really sticky Scotch stuff that is like fabric velcro but is much stronger?"

"Yes," says I.

"The stuff that if Chuck Norris were made of velcro, he would be made of?"

"Yes," says I.

"Why do we keep referring to ourselves as 'we'?"

"No idea," says I.

Needless to say, I went with simple and easy. If this works I will figure out a more permanent mounting solution. On the other hand if this kick-ass velcro stuff holds up, why bother?

[tirwin]

Next it needs a little juicy-juice. Ideally that will come from a switched 12v power source. It also needs a ground wire.

In the picture below, notice that there are 3 fused connections in the engine bay. You will have to remove the plastic cover to access them.



If you look at the left side of the bottom fuse (the yellow one), that one is switched power. The top two are constant power. This is where I decided to wire the power for the PLX sensor module. I used an inline fuse holder with a 3A fuse just to be safe to protect the electronics.

Do you see the two brown wires running in front of the PLX unit? Those are the ground wires. I crimped a ring terminal on the end of the ground connection and installed it there.

Now the unit can power up.

[tirwin]

Now that the unit has power, it's time to hook up the sensor. The O2 sensor has a 6-pin molex connector on the end. The only problem is that this thing comes with a gazillion linear feet of wire and I only need a foot. Two at the most.

Here's a pic...



If I'm going to shorten this wire, I had to find this same type of plug. I found it from a company called Waytek. You also need the little female pins that each individual wire gets crimped into.

Here are the parts numbers:

6 PIN RECEPTACLE MINI-FIT JR MOLEX PN 39012060
24-18 GA FEMALE TERMINAL MINI FIT JR MOLEX PN 39000039

I think there was a minimum number for the order. I can't remember how many of each. I ordered 20 of the connectors and 100 pins and it was about $11 + $5 shipping.

Now they also sell a special crimping tool for these types of connectors. I think it cost the same amount as our national debt. I might be a little off. All I remember was saying to myself "No way am I paying that for something I will use once in my life. Ok, twice if I screw it up the first time. Ok, third time's a charm, but I am not paying that."

So I used a pair of fine needle nose pliers and did the itsy bitsy crimps by hand.

I had some extra wire laying around and since I had quite a few extras connectors, I did a couple of trial fits. After that, I cut off the old connector and the excess wire. I then stripped back the sheath to expose about an inch of the 6 wires inside. I put a piece of shrink tube over the end and then started crimping the individual wires. Then it was just a matter of matching the same pin outs from the original connector and snapping them in place. Once I was done with that I heated the shrink tube to tidy up the install. Then I just needed to plug it in to the 6-pin connection.

Lesson: I could get a job in an Asian country working on an assembly line to build smartphones should this whole "corporate America" thing not work out.

[tirwin]

Took pictures of the old and new O2 sensor after all...

Old one:


New one:

[tirwin]

At this point the O2 sensor has been installed in the exhaust, the control unit has been mounted, it has power and the O2 sensor has been connected.

At this point, we have a choice for the next step.

If I had simply ordered the O2 sensor and control unit, all I would have to do is connect the narrowband output from the control unit to the wire going to the ECU on the 911. In my case, I also purchased the touch-screen AFR display gauge.

This decision makes a difference in how we wire up the next part. The base kit comes with everything you need to wire the narrowband output in a standalone setup. If you order the AFR gauge option, the extra wiring options come with it.

There is also a third option that works with either of the above setups. If you have a data logging device, you can wire up a connection from the control unit to send the wideband AFR info to the data logger.

What comes with the basic kit:


In my case I wanted to see if the AFR was within spec (I suspect it is running too rich) so I wanted to use the gauge to see the actual measurements. But since I'm also not 100% sure this is going to work, I decided to wire the gauge and leave it connected in the engine compartment while I do some testing.

To wire up the gauge, there are two connections on the control unit: (1) a 4-pin female connection on the unit and (2) what looks to be a standard female 3.5mm "headphone jack" type connector. Apparently this later connection is used for daisy-chaining multiple sensor modules together.

There is 4-pin male connector and male 3.5mm connector coming out of the gauge itself. Only two pins are used by default on the female end of the 4-pin connector on the control unit. These are presumably used to supply power to the gauge. The other two are used for (a) the narrowband output we will be connecting to the ECU and (b) an external data logger (again, optional).

There is a gray wire included with a pin connector already attached to one end. Simply slip this into the 3rd pin position on the connector (it is the one labeled TERM next to it). The instructions are pretty clear.

The other end needs to connect to the wire going to the ECU. More on that next.

[tirwin]

Normally there is an O2 sensor connection just below the fuel filter on the left side of the engine bay. I say normally because there are two kinds: the kind that has already crumbled and broken due to age and heat and those they have yet to but certainly will one day.

This is what mine looked like:


Bob Kontak helped me decipher the wiring to the ECU on my '83. There are two pins on the ECU for the O2 sensor. A ground wire and the wire that carries the narrowband voltage reading (.1-1V) to the ECU. I had read some strange things about this wire. Some of which was pure hogwash. In another thread, I learned that this wire from the engine bay to the ECU was actually a wire inside a wire. The outer wire acts as a kind of shielding to prevent outside interference from mucking with the voltage reading coming from the O2 sensor. It is less than 1V after all, so a little noise or interference could make a difference.

Anyway, so since mine was all crumbly, I decided to see if I could take it apart and see for myself. That way I could also close the case forever on the urban legends surrounding this wire.

First I cut it in a cross section across the wire. If you look closely, you can see that it is a wire inside a wire.



Then I cut it along it's length. In this picture you can see that the outer wire just terminates into the plastic and it doesn't connect to anything. The inner wire then extends a little further and is soldered to the metal tip. My connector was frayed so I broke the remaining plastic off the tip so you could see what's on the inside.

[tirwin]

In order to finish wiring up the narrowband connection from the PLX unit to the ECU, I simply cut back a little bit of the outer wire sheath and slid a piece of shrink tube over the end of it and heated it up.

Then I used a Posilock connector to connect to the grey wire going to the narrowband output of the 4-pin connector.



Finished connecting the "headphone jack" connection to the gauge and we're done.

Next step is to crank up the car and see if this works.



IT'S ALIVE!!! And none of the magic smoke came out!!!



I took the car for a quick drive. I got min readings of AFR 10.0 and max of 14.6. It wasn't a really long drive, so I'm not entirely confident that I got the engine warmed up enough for the sensor to be doing it's job, but given that I got a reading of 10.0 I think maybe I did.

Anyway, I need to do some experimenting with it to see if everything seems to be working properly. If it is, then my next project will be to run the gauge wiring into the cockpit and find a good place to install it.

Ok, I think that's it for now. Hopefully, this will be a help to others and feel free to ping me with any questions.

[Reiver]

Readings fluctuate with load and air temp....very hot in Arizona summers my afr is 13 to 13.5...now that it is cooler afr is 13.75 to 14.2.
It does help to know exactly what your fully warm idles CO/afr is set at for a start point and compare that to your reading.
I've SSI's so my lambda reads only one bank.

[tirwin]

Thanks, Riever!

This has all been part of the process of getting some things sorted out with the car.

As you say, I need to get it baselined. Tony rebuilt my WUR. The O2 was apparently disconnected for quite some time.

Thinking about getting a local shop to test CO and adjust AFR. Or by a Gunson and do it myself. I am trying to save up for SSIs and new exhaust though, so I'm still thinking about which way to go.

Is the AFR at the high end of your ranges when the car is warmed up and idling?

[timmy2]

tirwin,
It appears you are taking measurements of your AFR before the cat from both banks, you can adjust your mixture using your new gauge.
No need for a gunson..

[4flyboy]

Two beers Tirwin? Freakin hilarious, especially the part about your "moment of clarity"

Pardon my ignorance but what are you trying to accomplish?

I assumed that you were trying to determine if the mixture was rich. Why would you wish to mount something permanent to indicate this?

Is there a way/need to adjust this on a regular basis?

Thanks, very interesting but I'm clueless.

Scott

[timmy2]

He has analog and digital output, the analog performs the function of the old O2 sensor for the engine control system (Lambda). The digital he can use to observe and fine tune the mixture.
Well, that's what I would do...

[Reiver]

Originally Posted by tirwin

Thanks, Riever!

This has all been part of the process of getting some things sorted out with the car.

As you say, I need to get it baselined. Tony rebuilt my WUR. The O2 was apparently disconnected for quite some time.

Thinking about getting a local shop to test CO and adjust AFR. Or by a Gunson and do it myself. I am trying to save up for SSIs and new exhaust though, so I'm still thinking about which way to go.

Is the AFR at the high end of your ranges when the car is warmed up and idling?

Since you have a single outlet you should be fine as is....I still wanted mine checked just to make sure it was correct. If you do, find an indy shop with a computerized set up that preps cars for emission testing that has a recently calibrated unit.
It runs richer at idle and leaner at higher rpm.
I run mine a bit fat (rich) for the 9.8-1 compression.
It seems to like about 14 afr under load. My CO is set at 3. at idle.
I may be leaving a few HP on the table that way but in our AZ heat and that comp. ration it's a safety thing.

[tirwin]

He has analog and digital output, the analog performs the function of the old O2 sensor for the engine control system (Lambda). The digital he can use to observe and fine tune the mixture.

Well, that's what I would do...

What he said.

Plus it can be hard to know what's going on with AFR at times in the CIS troubleshooting process . This way I can get direct feedback to any changes I make.

And that gauge is cool.

[0396]

Bought mine via Richard Clewtte engineering - website. After install, it was like having my own dyno as I can see the results of the changes to the webers. Great product!

[tirwin]

I didn't know Clewett sold PLX. I bought my plug wires from them.

[tirwin]

Kent,

In another thread I documented what happened but the narrowband output was found to be incompatible with the K-Jetronic ECU.

And then shortly after that the PLX box died. I have since heard others complain of "infant mortality".

I have an Innovate Motorsports LC-2 new in the box that I plan on installing with a gauge but not using with the ECU. I have a test pipe that I'm going to get a 2nd bung welded in so I can still keep the stock narrowband.

[papamamapup]

oop!! accidentally delete my post!!

I will mount the oxygen sensor that came with GEN4 separately so, I won't mess up Lumbda unit.

Thank Tirwin,