O2 sensor?

[bikin' Ed]

I sure miss the old days with no extra electronics on my car... So, I'm here for some suggestions. Check engine light came on--code says O2 sensor (there are 2), map sensor, vaccum leak. Since the light came on, the car falls flat on it's face when I try to accelerate w/ cold engine. I'm guessing that the heater in the sensor is shot. After the engine is warm, I have no problem.

Mazda sites say that usually the front O2 goes and the rear, almost never. I replaced the front sensor last summer, and the car has only seen about 3500 miles since.

The car is a stock 1997 Mazda Miata, with a 1.8L FI engine.

Over the weekend, I checked the intake ducting, cleaned the IAS and PVC valve, and made sure that there were no odd vaccuum leaks.

Input greatly appreciated. -Ed

[SVOboy]

You might have gotten a bad sensor. It happens. I would try swapping with someone who has a working one just to check.

[wagonman76]

Check the wiring connector too and make sure the connections are firm. I have had several go screwy on my cars, including the one for the O2 sensor.

[tasdrouille]

Any reason just why O2 sensors go out? Carbon fouling? Why not try cleaning them?

[wagonman76]

Don't know but I have read that trying to clean them ruins the element. Not sure of the truth behind it.

[Ford Man]

A mechanic friend of mine told me you could soak the 02 sensor in Sea Foam over night to clean them without doing any damage, I have never tried it so do it at your own risk. Another option is going on eBay and searching universal 02 sensor, they can be bought for about $20. each, you just have to cut the plug off your old sensor and splice it on the new one. I put them on a '96 Contour several years ago and haven't had any problems with them.

[hamsterpower]

I've had a similar problem in the past, turned out I forgot to torque the O2 sensor and it vibrated loose.
I've also used a universal sensor from Bosch. 5 years no problems. (except needing to be torqued after a few months of weird symptoms.)

[Southcross]

a few things can kill an O2... Rich mixtures, excessive exhaust heat, carbon/oil fowling, one sure way to kill an O2 is getting anti-sieze on anything but the threads.

if you have any kind of air leak, intake or exhaust, it can trip the Oxygen sensor into believing the engine is suddenly running lean... tripping the CEL

[tasdrouille]

Why don't you try swapping the O2 sensors? If your front O2 sensor is the culprit the code will change to tell you your cat is bad, but performance should be restored when the engine is cold.

[Southcross]

Originally Posted by tasdrouille

Why don't you try swapping the O2 sensors? If your front O2 sensor is the culprit the code will change to tell you your cat is bad, but performance should be restored when the engine is cold.

some cars use completely different sensors for the front and back...