How to check for a bad 02 sensor? I'm running rich

I posted some Q’s in the technical thread, but it’s lame having to wait all day for something to be approved when it’s actually car related… on a car forum :bloated:

Anywho, this is just an added Q to that one that’s slightly more important.

I was trying to find out why my car was running rich(got the car last winter, didnt bother/care). Went through all the hoses, found 2 or 3 that led to nowhere, but those are for the ac system ( previous owner took it out) none of them pull a vac.

Then I spotted a single loose wire, and low and behold, took a close look at the o2 sensor (out of the manifold). So thats where it goes. Connected it back up aaaaaaaand… nothing. No change. Shouldn’t the engine light have come on if that was disconnected to begin with? (never was) Is there a way to check to see if the o2 is bad?

It’s a 1990 rice bur… I mean… 240sx

Spanks mang

well, technically if it was a bad 02 it should have thrown a code. only way to check is to test it with a multimeter or just replace it and see if there is a change, hopefully its not that expensive for a 240

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well, technically if it was a bad 02 it should have thrown a code. only way to check is to test it with a multimeter or just replace it and see if there is a change, hopefully its not that expensive for a 240

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That kinda irks me. If the thing was completley disconnected before, shouldn’t it have thrown a code? The car gave no indication that anything was wrong other than me getting high of the smell of gas

yeah you would think, sometimes cars are funky, polus its pre 95 so you never know. maybe the bulb for the light is shot? lol. are you SURE its rich? or do you just have a modded rather open exhaust pushing alot of carbon?

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yeah you would think, sometimes cars are funky, polus its pre 95 so you never know. maybe the bulb for the light is shot? lol. are you SURE its rich? or do you just have a modded rather open exhaust pushing alot of carbon?

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um… yeah it’s one of those diy manifolds actually. It’s louder than poop, I just welded in a new muffler with no luck, now I have to find some time to see if the cat was punched. Either way the manifold has rinky dink pipes, so I don’t know. Yes, there is carbon build up as well, but what I’m smelling is good old gasoline, very prominently actually. Who knows, I haven’t had to take care of this issue before, but I’d like to do something about it.

well, if the cat is hollow its going to smell more like gas. is this car turbo? im just asking that based on your Diy manifold statement. if its a turbo car that is a whole nother set of variables lol. does the car have an adjustable fuel pressure regulator or anything like that?

maybe see if you can borrow a wideband from someone just to get an acutal number as to what the fuel ratio actually is

Use a scanner and see if its switching. Or use a dvom and check it. Its early obd1 so i’m not sure if a late model scanner would work(you may need to find someone with an old monitor 3000 or 4000. You should be able to check voltage at idle then bring it up to 2500-3000 and see if there’s a difference

check the 02 sensor voltage

Yeah, I was going to say, check the voltage, or use scanner. But, if u cant get either one of those, just replace the sensor. Then, at least u know its new. (Stay away from Bosch) they are pretty weak, Denzos are nice.

Oh, did this car have a 2nd O2 sensor…like to let the pcm know there was a cat. conv. there?