Drive with or without an unattached oxygen sensor?
 

Is my car safe to drive?
My husband cut an oxygen sensor and stripped the threads trying to get it out, only to realize it wasn't bad (car's at 67,000 not 100,000 miles and just passed a safety inspection)....So he pushed it back in place without reconnecting or rethreading it. Is the car safe to drive this way? Can the sensor be reattached? Should I take it out to drive to a mechanic? If it falls out will it hurt the engine? There are two oxygen sensors should we replace both now, even though they should have been good for 33,000 more miles?

I'd say if it falls out, you'd have a noisy exhaust at the very least, and you could have dangerous carbon monoxide leaking into the the interior of the vehicle. Also, when it falls out, iit will no longer read properly so your Check Engine light wil come on, and your car will switch to a set of default parameters to run on, which will mean you'll probably get less mileage.

The best course of action is to replace the O2 sensors. and hopefully your husband has learned to not mess with stuff unless he knows what he's doing.

-Jay

I did this once (stripped the threads)- thankfully the threads came off the O2 sensor so I just had to use the correct sized tap to get them out of the exhaust manifold. After tapping, the threads were back to normal.

It won't hurt the engine, but you may melt some nearby wires if they are close to the escaping exhaust gasses. You could also possibly start a fire if that area of your manifold is soaked with leaked oil.

You need to get it fixed- but I drove mine for a day (at low speeds) with a chunk of wadded up aluminum foil stuffed in the hole with a wire around the manifold to keep this plug from being blown out.

Drive with or without an unattached oxygen sensor?
 

Thank you for your replies!
My husband put a screw in the old one, but since the 4 wires are cut, the service engine light is back on. I did not know that the service engine light being on changed the workings of the car. Jay, thanks for that information.

Do you know where we could find the schematics for a 2002 Mitsubishi Diamante so we can discern which is the rear O2 Sensor? We are going to Heely thread(?) the stripped area and replace both sensors...if we can figure out where the "rear" and "front" are.

I did drive it today, gently, and I did not notice anything alarming. Do you think we could pull a boat with only one working O2 sensor and the service engine light on? I am afraid it will be weeks before hubby will have time to fix it.

the check engine light doesn't affect how it runs. the fact that your o2 sensor isn't there (according to the car computer) changes how it runs.

the o2 sensor is the feed back part of the closed loop. the car senses the air coming in (different ways depending on vehicle), it then throws in a certain amount of fuel depending on the reading from the input sensor (MAF, IAT, etc..), combustion happens and exhaust gas is released, the o2 sensor gives feed back to the computer to tell if it did it right.

without the o2 sensor, the computer doesn't know if it did it right (that is overly simplified) if it doesn't know how it is doing, it goes to a preset within the computer that usually runs a little rich. this kills your fuel economy most of the time. I have heard of people losing 5 mpg because of a bad o2 sensor.

as far as where they are, the front o2 sensor may be on the exhaust manifold but it is definitely before the catalytic converter. the rear is after the catalytic converter (in some rare instances, it is in the cat). a google search should tell you everything you need to know. as far as which ones to buy, I would go to advance auto parts or autozone and they can hook you up. both of them are online as well.

the towing is a funny one. I personally wouldn't tow with a vehicle that isn't functioning properly but I don't really think it would hurt it. just don't tow 20 tons or anything too out there. please don't take my word for this last part, only you are responsible for your vehicle.

good luck

It's probably gonna run a bit rich without the O2 sensor, so there might actually be less risk of ping while towing in hot weather, but over a longer period it will tend to carbon up the motor and increase risk of ping again.