O2 Sensor

[DogDoc]

Hi all!
I had my timing belt tensioned today and had my mechanic look at the exhaust to check if the exhaust test pipe (?) had the proper cap/nut on it (thanks Scott R!). No nut, so that may be the excessive noise that I'm hearing from the exhaust. What he said that he also found was that the O2 sensor was butting up against the transmission. He relayed to me through the shop owner that it was his opinion that if the O2 sensor wires or connections got too hot from the tranny, it could cause a short and take out the DME system. Now granted that he is not a certified Porsche mechanic but has worked on a number of Porsches:

#1: Is a short through the O2 sensor likely to wipe out the DME computer?

#2: How hot does the tranny get? Can it melt the wiring from the O2 sensor?

I took the car back to the muffler shop where I had the aftermarket cat installed and they got it up on the rack and....

#1: The O2 sensor is not jammed against the tranny; there is about 1/4" or 3/8" clearance. This brings up the question...

#2: What is the normal stand off from the tip of the O2 sensor to the tranny? The aftermarket cat that I bought was supposed to be a "bolt-on" replacement. I assume that the design would account for the O2 sensor location.

I'm inclined to believe the muffler shop that the clearance is adequate to prevent any problems, but still....a new DME can get prettly expensive.

Thanks in advance for the info!
Mike

[AFJuvat]

Run from the shop.

Tranny heat has nothing to do with O2 sensor operation - the tranny is in the rear of the car, the O2 sensor is behind the engine. I think you/the shop is talking about the torque tube - Which gets hotter from residual exhaust heat than on its own

For that matter, the O2 sensor has an internal heater by itself and is insulated against external heat (hard plastic insulated wire), not to mention that exhaust gasses are a few hundred degrees as it passes the O2 sensor.

Depending on your mileage, you are probably due a new O2 sensor, but the shop's assessment is, in my opinion, ludicrous.

AFJuvat

[DogDoc]

Thanks for the quick reply!

I'm probably due for a new sensor anyway, so I may just replace it. I read a previous post on testing the sensor; it sounded to me that if you unplugged it from the engine compartment that you should note a change in the idle if it was operating. A bad sensor would explain the sluggish performance that I'm getting. My mileage has not been too bad (25 mpg primarily city) but I gusess it could be better.

Thanks again for the info!

Mike