Emissions issue w/ '93 B2200 (Carbed)

Try hr for some additional help:
http://www.troublecodes.net/mazda/

So im getting two trouble codes. A 15 and 16. So i have two questions.
A) does anybody have wiring diagrams/pictures of their o2 sensor connector?
B) will a malfunctioning o2 sensor set off the egr position sensor malfunction?

As to the wire, remove the electrical tape; if the connection is soldered, then good, re-wrap to cover the worn area.

Typically, high NOx is due to EGR valve, and you said you cleaned yours. Did you check it for operation with a hand vacuum pump afterwards to make sure it actually moved, and also check to make sure it was closed when no vacuum is connected/applied? I've got two used and working B2200 EGR valves available if you're interested, very reasonable - my 1988 B2200 has a Weber carb and a block off plate for the EGR so I don't use one, and no emissions test for me.

One test for a bad EGR valve itself is to start engine, plug the EGR vacuum line coming from carb, pull hand vacuum on the EGR nipple, and the engine should stall or practically stall when you pull that vacuum.

As far as your O2 sensor is concerned, you can remove it, and clamp it in a vise, and then use a multimeter positive connected to the green conector on the 20 VDC scale and grounded with where it screws into the exhaust manifold and then using a propane torch, heat the tip of the sensor to test it. As it gets hot it should generate voltage that the ECU should see when it is normally hoked up to the engine. You could do the same test with it still installed in the manifold but it would probably take longer to heat up. These trucks don't use a heated O2 sensor so until the truck is warmed up the response on the sensor is sluggish. As I recall, where the wire goes into the ECU it is foil wrapped so you could test for the signal there to make sure there isn't a break in the signal somewhere.

As far as your EGR signal, there is a single wire potentiameter that tells the ECU that the EGR is receiving an operational signal from vacuum operation. If the ECU doesn't receive both the EGR and O2 signals it won't go into closed loop and your gas mileage will go into the toilet.

To clear your ECU codes disconnect the battery and then step on the brake pedal to discharge any residual voltage.

Ok o2 sensor checks out and now i am still getting a 18 code. I'm thinking the wire that is exposed connects or grounds to something. Can anybody confirm?

If I am recalling this properly, the wire that you are referring to is for shielding only. The O2 sensor on the trucks is a single wire only, but because it runs along hot metal and because it is so long, Mazda put the wire inside a non-conductive insulator.

I went back to troblecodes.net and the 18 refers to what they call the "air-fuel solenoid." That is the mixture control solenoid that is supposed to vibrate inside the carburetor to atomize the fuel. If it doesn't work, the carb runs rich and that might be why you are flunking your emission test. The good news is that you are making progress in tracking down your issues. The solenoids go bad over time and get stuck. I had to replace mine because it quit working. The solenoid is located inside the carburetor at the front and it has a two wire connection. It gets activated when the truck is trying to go into closed loop operation (the engine warmed up and the other sensors are working) It is likely it wasn't replaced when the carburetor was rebuilt but the good news is that it still is available at the dealer or when mine went bad, I got one at the Missan dealership. The same solenoid is used in Datsun 510 carburetors, so maybe it night be cheaper there. But if you bought a reman carb, you can take it back with this information and get a replacement.

An A.S.E tech.

Do you have a multimeter that can measure dwell? If you do, there is a way to check to see if your MC solenoid is operating at all. There is a green square plug as I recall on the passenger fender about 18 inches from the battery that you plug the positive meter probe into and then ground the other lead. You will need to set your scale on your meter to 90 degrees. With the engine warm and running, the meter will start at 90 degrees and then start to count down to zero. If the solenoid is working dwell should stop the countdown at 45 to 55 degrees. If the solenoid doesn't kick in, the countdown will continue down to zero and then default to 90. You can rev the engine and start the process over, but I think your code 18 means the computer has already tried to reset the solenoid and it isn't responding.