How bad is it to run with only 1 O2 sensor??

N8Miller

I need NOS....make it 2 of the big ones
Founding Member
Jul 26, 2000
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Kingston, PA, USA
Ok, i have to reroute the wiring for the sensor. I have been running around (about 60-70 miles tops) with only 1 in becasue when i switched to longtubes, only one was long enough. i am going to find a way to wire the other one in tommrow, but i was wondering if i did any damage or not? the motor runs strong---but i can tell it needs the other O2.
thanks
 
i think it goes into a default mode if there is one or more missing o2 sensor(s). it should be fine (no worse than having a wire get chafed/cut).
 
You're running in closed loop right now, so it's running pretty inefficient and rich. Worse thing about it is the exhaust leak where the sensor is supposed to screw in. Other than that, your car should be fine.
 
we put long tubes on a friends 89 lx, he forgot to order the extensions, so i bought some wire $4, connectors $2 clipped and extended his. never had a problem. even on the dyno, air/fuel was correct. those extensions are pretty high. good luck
 
you're actually running in open loop right now and based on rpm and load % it is using the open_loop_stabalized_fuel table (that's not quite the exact name).. so if your A/F is accurately tuned with your AFPR, then, when the EEC commands 13.95:1 for example under 60% load @ 4000 rpm then it should be okay.. the exhaust leak part is what I'd be more worried about long-term... but that's why you feel more powerful since you're running a more rich A/F compared to the Closed Loop (re: both o2's working) target of 14.654:1...
 
well reading this makes me wonder if one of my O2's is bad. I replaced 1 about a year and a half ago cause it was stripped out (was swapping h-pipes) and for the past 8 months or so I've been getting lower gas mileage than I think I should and it smells rich. is there any way to check if the old one has gone bad? or is it basically just one of those "buy and try" things?
 
I just found out that the reason my check engine light was on for about 3 months is because one of my o2's wasn't connected...I pulled both out and burned the ends off with a propane torch (coleman bar-b-q) made sure they were hooked in this time and DAMN! the car seems to run stronger and the gas milage is waaaay better now..and the best thing is that I dont have to look at that damn check engine light anynmore...
 
I put longtubes on my fox 2 days ago. Didn't realize the sensors were too far away. I just cut my plug-ins, ran 1 foot of wire from the sensor to the plug-ins, taped them up well, and put some wire wrap on them. No engine lights, runs sweet.. Longs tubes and Dr. Gas are made for each other.
 
IMPORTSMOKER said:
I just found out that the reason my check engine light was on for about 3 months is because one of my o2's wasn't connected...I pulled both out and burned the ends off with a propane torch (coleman bar-b-q) made sure they were hooked in this time and DAMN! the car seems to run stronger and the gas milage is waaaay better now..and the best thing is that I dont have to look at that damn check engine light anynmore...

what purpose does burning them have? just to get all the old carbon and junk off? maybe I should try that...

and what kind of gas mileage were you getting with one unhooked? I get like 14mpg but I'm sure it should be more as I only have light mods - and it just reeks of gas when its running
 
I found out the other day that I only have one 02 sensor hooked up. I get good gas milage though, and the car seems to drive fine. No check engine light or anything coming on. I bought a new sensor but I have to drill a hole for it in my exhaust and everything. I'm not sure if it's worth it or not.
 
Are the O2 sensors necessary?

I'm swapping a 5.0 into another vehicle without any of the smog stuff or a cat. Does the 5.0 computer need an O2 sensor to function properly or does the lack of O2 sensors put it into Limp mode?

Thanks,

Bob
 
Bob,
if your swapping it and keeping the fuel injection, yes, i think you will need an o2 sensor.

Update:i spliced the wires and made them longer. it must have worked good becasuse it runs hard now and the idel has gotten better...so has the acceleration.
 
Qwk88LX said:
I replaced my busted O2 sensor, I think I'm getting better mileage..kinda hard to tell since I've got my C4 in now & I dont have OD...it does idle a lot better now though :D

My car will die in cold temperatures when I start it. Maybe it's because of the one O2 sensor...or maybe its the cold. My truck will run like crap in the winter, while in the summer I hardly have to even turn the key to start it.
 
_JB_ said:
My car will die in cold temperatures when I start it. Maybe it's because of the one O2 sensor...or maybe its the cold. My truck will run like crap in the winter, while in the summer I hardly have to even turn the key to start it.
when the car is cold, the lambdas are not used. they begin to be used around 178*, IIRC.

your problem sounds more like an out of calibration ECT or ACT sensor. if it is telling the puter your motor is warm, when the motor is indeed cold, the mixture will be too lean. the sensors can be within spec (no code), but not proper for the situation (as above - telling the motor you are warm when you are cold).
you can check the values of the sensors with a DMM. good luck.