HELP! - O2 Sensor (Lawrence and Dennis)

geoffbaltz · geoffbaltz's Garage

I think my O2 sensor went bad.

Should the car run different when at idle and at operating temp when unplugging the O2 sensor?

86 951

-g

ruechaos · ruechaos's Garage

As I understand it, this is my interpratation. Correct me if I'm wrong please.

I would believe that it would run slightly different as the O2 sensor works with the dme to ensure a proper fuel to air mixture, which will also effect the AFM and you may not be getting the right amount of air. If the O2 sensor goes out, I would assume that the lack of information would be interperated by the dme as that not enough fuel is being injected, and the car would run rich. This was the case on my n/a. You really couldn't tell too much of a difference in performance or idle, but you sure could smell it, and see it, as the gas milage wasen't as good as it is now that I changed the sensor.

-Tony

geoffbaltz · geoffbaltz's Garage

Yes, the car would run rich. Yesterday, Mine started to backfire and would barely idle yesterday. It rained cats and dogs here in St. Louis on Monday and Tuesday and my car was outside. I didn't try to drive it until yesterday.

I just got back from a test drive and it is running fine and strong as ever! Hmmmm. I think something is getting wet! This throws out the O2 diagnosis.

Anyone else have water problems? This is strange.

-g

JonA · 06-14-2002, 05:29 PM

I would look at the dist. cap, rotor, and wires befor getting into anything complicated like the O2 or injection problems.

Jon Aborn

DennisR_944 · 06-16-2002, 05:37 AM

With the car idling and at operating temperature, unplug the sensor. If there's no change in the idle, then chances are that it's bad. Your gas mileage will suck and you should have a distinct sulfur like smell from the exhaust. The exhaust tip would be black from running rich.

arnebret · 06-16-2002, 06:28 AM

I just tested mine. Just unplug the connection of the sensor. It's in the middle of the engine bay, right behind the intake manifold and just before the firewall. You can take it out, unplug it, put a voltmeter in the little hole with #1 next to it. Ground the other wire of the voltmeter on the neg-pole of the battery. It should indicate somewhere between 0.1-1V Mine did about .437V
The higher the voltage the lower the amount of oxygen in the exhaust. In other words: high voltage means rich, and a lower means lean.

In my case about 0.5V is about 14.5:1 A/F mix. The range from 0.8-0.2 volt is very sensitive, and all but linear. Have a look at this:

If you get nothing, or a strange reading, replace the bugger.

PS: If you run a tuned, high-boost 951, be SURE to have a functioning O2-sensor. If not, quite ****ty things like knock etc. might occur as the DME cannot adjust settings realtime.