My A/F ratio gauge hasnt been working so I decided to figure out why, cause my car has been running a lil rough and I'd like to have some sort of idea how its running. It has power but the gauge wouldnt indicate anything. So I started tracing the sigal wire with a digital mulitimeter. At the wire coming in from the oxygen sensor I got 0. Nothing. WTF? So I went directly to the oxygen sensor with the car running and tried to get a reading from it directly. 0 volts. Again WTF, cause the sensor is a brand new bosch sensor. I disconnected the signal wire from the gauge and *PING* the gauge lights up. Now I'm really confused. Could this be the reason my car idles like ****? But wouldnt the sensor at least read SOMETHING? Also, which wire at the ECU is the oxygen sensor wire?

 

At idle O2 sensor inactive. Let's put it this way, ECU not reading signal from O2 sensor for idle purposes. S5- O2 sensor pin 2C. Middle plug on the ECU, and the top pin second from right. Black wire. From manual-Idle below 1.0v, acceleration .5-1.0v, deceleration 0-.4v.

 

the o2 sensor still sends a voltage regardless of whether the ecu chooses to use it though.

 

replace it with a Bosch universal, works fine and only cost $32 USD

 

I had a bosch universal in it. I just replaced it today. Still not getting much of a reading out of it, although once the car warmed up I started seeing 0.04 volts. Let me ask this question. It takes time for an oxygen sensor to heat up to put out a reading right? So a full 3 inch exhaust and no emissions may make the oxygen sensor take longer to heat up due to the less constrictive exhaust being cooler?

 

my o2 sensor does not connect to anything, how should i go about finding the wire that it connects to?

 

.04 volts is essentially zero. At idle mine mine puts out between .3 and .5 volts. If you unplug it and measure the voltage you should get a reading around .3 volts.


Rob

 

i like to know this as well..the previous owner just yanked it out and taped it to the harness without connecting it.......what a bastard.

 

Dear World of RX-7 owners. IF you have your emissions working (read ACV w/Airpump) you will NOT read much of anything at idle. Why? Because the acv at idle is directing WHAT into the EXAUST PORTS? Yes. Air. Air from the AIRPUMP. And where is the 02 sensor in relation to the exaust ports? Yes. Downstream. What will large doses of freah air do to the 02 sensor? UH huh.

So if you do have the airpump and the emissions system and have a non-turbo car...then pull the BLUE connector off your RELIEF SOLENOID. What happen. EEEEEk! THe sensor reads much higher.

But if you have a TURBO car, then that won't work. SO what you do is, reach over to the acv and remove the vacuum hose that comes from the SWITCHING SOLENOID (you know, the top nipple that sticks straight up in the air), and remove that vac hose from the acv. That lets the poppet valve in the acv close off the passage to the exaust ports and EEEEEEK again. The 02 sensor should read higher.

Idle is in no way shape or form effected by the 02 sensor on a RX-7.

If you don't get the results as described above (fully warmed up engine), then your emissions have gone bonkers,**** up, fubbbered up.....ain't a workin. OR you have the shield on the 02 sensor touching the center conductor on the shielded wire going to the ECU. Pin 2D on a series four (The good series).

On a series four car, the 02 sensor wire was/is a shielded Grey wire. It runs under the dynamic chamber on a non-turbo series four, around the drivers side, back to the passengers side and on to the ECU at pin 2D. It's not all by itself by the time it comes around the front of the engine headed to the passengers side. It's in that big **** haness about an inch and a half wide. All wrapped up in braid etc.