Powerpack

I'm wondering what is the worst effect that could cause a faulty oxygen sensor? In most cars, the ECU is using O2 sensor only for fine tuning the mixture at low RPM and idling. Does it work the same way on rx7's or does the ECU use it all the time, at high RPM also?



Have you got problems at high power with O2 sensors?

13BAce

The ECU is only using the O2 sensor input on light throttle/cruise/idle conditions.

Powerpack

Thanks. That's what I was hoping and expecting and I just found something on the web that explains what you just said. I was asking because I connected a voltmeter on the O2 sensor today and it's always reading around 0.8 to 0.9 volts in most conditions except when I go off the gas on deceleration that indicates zero what is normal. It means the anti-afterburn valve is working but not the rest. Do you think 0.850 to 0.900 seems to rich even on full acceleration? It would explain the rather eratic power output of my car.



Here the link if someone would like to read it:

Air/Fuel Meter and EGT gauge

13BAce

Thanks. That's what I was hoping and expecting and I just found something on the web that explains what you just said. I was asking because I connected a voltmeter on the O2 sensor today and it's always reading around 0.8 to 0.9 volts in most conditions except when I go off the gas on deceleration that indicates zero what is normal. It means the anti-afterburn valve is working but not the rest. Do you think 0.850 to 0.900 seems to rich even on full acceleration? It would explain the rather eratic power output of my car.



Here the link if someone would like to read it:

Air/Fuel Meter and EGT gauge[/quote]

.8 to .9 sounds a little high. Check out the shop manuals at http://fc3s.org . They tell you the exact voltages you should be seeing at idle.

Powerpack

I checked in the factory manual but it's said 'under 1 volt' on idle, accel: 0.5-1 volt, decel: 0-0.4 volt. So I will try to find some reasons why the ECU is not switching in 'closed-loop' mode.

phinsup

Moved to the FAQ's, good post guys. :thumbs-up:

Chuck

Seeing as how this is archived, I would like to add my experience with a bad O2 Sensor. My '91 N/A is white and my exhaust was turning my entire rear bumper black with deposits. Way too rich! I replaced the O2 sensor and that problem went away.

matts86fc3s

if it wont go to closed loop mode check this: there is a little sensor on the bottom of the radiatior on the drivers side... i think its on the radiator... i dunno but look down there and youll see the sensor, thats what tells the computer to into closed loop mode

rmriggin

I guess this would explain my problem with lower rpm (almost stalling) at idle and when clutch is presssed in after car is completely warmed up. I know my TPS is set right and is good because I set it using the resistance method and then double-checked using the light method and both were good. One thing I was wondering though... Would it take longer for the O2 sensor to warmup with an RB header? I remeber with my stock header that it seemed to heat up faster and hold heat longer. Am I right? Or am I just smoking crack?! Thanks.

Guess I will find out when I change my 02 sensor in a few days if my idling issues are fixed.