On my 1990 Ej swaped rig I have the O2 sensor disconected(no exhaust Y for it to mount in) The car runs fine,idles about 750 rpm and its not throwing codes(at least the CEL isn't lighting up except on start up(although it is possible I dont have the CEL for the harness wired to the right wire in the clutster).But would no O2 sensor cause it to run poorly,idle rough,etc?On my 1990 Saab 900(its not OB1,I think) when its O2 sensor died the car could barley run the idle would swing 300 RPM up or down and it had no power.so Is it supposed to be like that?

Car may be staying in open loop. If it is it wont throw a code, but you will see poor gas milage (but there is always one that says they are fine) and the performance wont be as good as with a functioning one. Keep in mind performance means emiisions, acceleration, driveabilty and gas mileage.

 

nipper

Right on. It should work acceptably in open loop ableit with possibly not optimal mileage. It knows roughly/crose enough how much fuel is needed for the air coming in and the conditions. The O2 sensor just lets it control the A/F ratio with feedback. Maybe on the 1990 it's not an emissions item (i.e. an item 'requiring' the CEL.MIL to come on)?

I would verify that the coolant temperature sensor is working properly. If the ECM is seeing erroneous readings there, it may stay in open loop, as was mentioned already. I don't think the OBDI cars were required to achieve closed loop in a specified amount of time, so the ECM would probably run like that all day without throwing a code.

I would verify that the coolant temperature sensor is working properly. If the ECM is seeing erroneous readings there, it may stay in open loop, as was mentioned already. I don't think the OBDI cars were required to achieve closed loop in a specified amount of time, so the ECM would probably run like that all day without throwing a code.

 

Correct. OBDI cars have a differnt emission standard then OBDII.

 

nipper