SpeedRacer

Is there a way to test the signal coming off the O2 sensor to check to see if you are running rich or lean without having to buy an AF gauge? Can I can check directly off the ECU somewhere so I can check my mixture while I'm driving?

tesla042

http://www.ggimages.com/rx7/afmon.html

I think there's an ECU pin that the o2 sensor runs directly in to, but I have no idea which one it is..

-Tesla

HAILERS

Pin 2D on a 86 thru 88. Expect , while driving , for the figure to jump around continuosly(sp?). There will be a trend. It will be bouncing on either side of 40millivolts. There is a figure, 40 millivolts, that is what is called *stoic*. When you nail the throttle the figure will steady out because the o2 sensor is in *open loop*. It'll read a touch rich, something like 80mv. I do not know right now what pin it is on other models. Nice toy to play with. Also go to autometer.com and look under tech questions, I think, and there is a good description of the 02 sensor. EDIT..Go to this site http://www.fc3s.org/ and down the left hand column, there is a reference to the ecu codes for a n/a and a Turbo. They tell you what each and every pin on a 89 does. While doing the 02 sensor thing, just jump over there and look at the output of your TPS at idle and full throttle. Best and easiest way to see if your tps is correctly set. Here http://www.autometer.com/hp/index.html look under tech tip faq for how the 02 works. You probably already knew, but every little bit of info helps.

live4boost

iTrader: (2)

your still just taking readings from the stock 02 sensor, which will vary on the condition of the sensor and what not. It will tell you the same thing as the cheap gauges that you can get (auto meter and others.) It will tell you if you are dangerously lean or rich and you should not tune your car with this method. I you are worried about leaning out, take it to a shop that has a wideband 02 sensor(I think that is what it is called.)

mazdaspeed7

Even though the ECU goes into open loop mode, the O2 sensor will still give a reading of the A/F mixture, but the ECU wont use the signal to adjust the mixture. It has set maps for WOT.

But the 1 wire o2 sensors are only accurate at close to stoich. The farther you are from stoich, the less accurate a 1 wire o2 sensor is. The wideband o2 sensors have 4 wires, and RX7's cant use them without a box to convert the signal or an aftermarket EMS, such as Haltech.

live4boost

iTrader: (2)

wait doesnt a dyno use a wideband o2 sensor. Well whatever it uses that is one way to tune your a/f, and though it is pretty pricey it is a lot more accurate than the other way. Then if you can do the street tune after to fine tune

Keith

OK, for your '90 GTU, the O2 sensor pin is 2C, which is the 13th pin from the right, top row. Here is a thought, though. On 87-88 cars, they had an oxygen sensor output on one of the test connectors, along with code readout pins. This test connector was eliminated in 89, instead all the codes were flashed through the check engine light. Since they had this function in 87-88, they probably still have it in 89+ cars. How would you get it to display? I suggest this: Start the car with the test connector (Drivers side engine bay near the leading coils, a green single connector) jumpered to ground. Rev the engine to about 2000 rpm. If the light starts blinking at about a 1 second rate or so, you are looking at a representation of the O2 sensor output. Here is an interpretation of the lights:
Off is lean.
Fast blink is a little below stoic.
1 second blink is stoic.
Slow blink is a little above stoic
On (no blink) is rich.
You should see the check engine light on (no blink) under WOT. It will probably be off at idle, due to port air injection. You get the idea.

Please let us know if this theory of mine is correct. I will also try it on Keith's buddy's 90 to see if it works, and post accordingly.
Peace!

Irv, Keith's dad