3.2 Carrera runs better with O2 disconnected...

My 1988 Carrera seems to run better when I disconnect the O2 sensor. It hesitates a bit when it is connected but the hesitation goes away when I disconnect it. Is it time for a new O2 sensor? Or just leave it alone...

I have a 85 carrera with the same engine as you. My car runs better with the 02sensor disconnected, but gets bad gas millage. You can check the output of the o2 sensor with car running with a volt meter. You should see a swing in voltage. I personally think that the motronic dme has a few design flaws for the us spec cars. The unit was designed for germany with no emissions. Then you add emissions and end up with a none perfect fuel metering system.
Good luck!
DRD 85 Carrera

I was unaware that Germany has no emissions laws for their cars! Must be really smoggy there.

Your car should not hesitate with the O2 sensor connected. I think you have another problem that is causing the hesitation, and by disconnecting the O2 sensor, you are causing the DME to default to full rich, which is helping to mask the problem.

The O2 sensor is designed to get the car to run at 14:1 air fuel ratio, which is the ideal ratio for combustion.

If it were my car, I would try to get it to run right with the O2 sensor connected, the way it should.

I agree. Proper fuel/air mixture is essential. Lean mixtures make your combusion chamber (pistons, valves, etc) too hot and those parts can burn or melt. Too rich and you will plug your expensive catalytic converter. I, too, suspect the problem is elsewhere. Make it work like it was designed to work. it's hard to build a better mousetrap than the folks in Stutgart did.

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'83 SC

Thanks for the advice. I will follow up and check it. What do I connect the voltmeter to to check the O2 sensor? What readings should I get?

As an aside, what if I wanted to remove my catalytic converter and just run a pipe? In South Carolina we are not required to have inspections so I can do this. Who sells the pipe? Would I notice any performance improvement?

thanks!

Bruce Anderson tested the cat replacement pipe on a dyno, and found no gain in power.

I don't think it would hurt, though, and may help if your cat is older and perhaps not flowing as well as new.

Most test pipes (like the ones commonly available and made by Bursch, for example) have a fitting to screw the O2 sensor in!

Just about any mail order place should be able to get the Bursch test pipe.

The O2 sensor MUST NOT be tested with a cheap, analog meter from Radio Shack or anywhere else! It must be a 10 megOhm or higher digital, or FET-input (or vacuum-tube) analog Voltmeter, and the signal is in the 100 milliVolt DC range. The actual signal level is not terribly important, as long as it is varying as the engine is running, as you change rpms, and throttle opening.

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Warren Hall
1973 911S Targa