O2 sensor help

[JimB]

I have been chasing my tail for two days now. Come to find out there is a difference between 1987 early 4.0 and later 4.0 O2 relay location and wiring. Early O2 sensor relay is in the rear bank of relays. Not the front. It only has 4 wires instead of 5. REM II says no O2 heater voltage. Sensor does not cycle like it should. Installed new NTK yesterday. Same problem. Trying to find wiring diagram for early 1987 O2 sensor.  My relay is wired as such.  85/ORN,  86 BLK/YEL, 87A GRY, 87 ORN. Any help would be highly appreciated. 

[fiatslug87]

Download the 87 electrical manual from here 

 

[JimB]

Thanks a million. The 87 manual shows the O2 relay 4 wire. Just what I needed. Again thanks. 

[JimB]

Fixed and confirmed all wiring. O2 sensor works according to the REM II. Cycles goes into closed loop. All seems good. Then I drive it awhile and the O2 signal freezes at around .33 goes into open loop. Let engine cool a bit and it starts working again. Drive it again engine heats up and back to open loop. Does this sound like a bad O2 sensor? Is there another sensor that can cause this? Going to swap in a Bosch I just bought and test. Any ideas???

[fiatslug87]

See this post and linked posts 

 

[Ωhm]

Using your REM, post up your STFT and LTFT numbers.

[JimB]

Sorry for the delay. Had to change tie rod ends. Was not sure if needed to be driven.  STFT 60-80 up and down. LTFT 126

Jim

[JimB]

I also replaced the NTK with a Bosch and the numbers cycle like they should (O2). Stays in closed loop now.