Front O2 sensor probe with LOTS of white dust... stock except for APR trial flash.

[Jer]

Just curious what would cause such a lean condition. It looks like there is plenty of black on it to indicate a slight rich condition pretty customary with stock tuned vehicles. On top of the black is a pretty fair amount of white residue indicating that recently it's been running lean. This is a 2007 A4 w/only 30k miles on it and the ONLY modification I have done prior to pulling this O2 sensor was having the ECU flashed with the APR 6hr trial program. It seemed to run quite well and from what I can tell he had it set in the 91oct mode which should have been fine. If he somehow set it to the 93 or 100 octane mode it would be an explanation of this lean reading but as I already stated I'm relatively sure he had it set to the 91 octane program as it should have been.

Needless to say this has me a bit concerned and since I'm getting ready to mod and run higher boost and possibly methanol injection I want to make sure I can track down the cause of this. Anyone else ever seen this on an otherwise stock car?

[Jer]

Here are the pictures I just took:

[Grishbok]

didja taste it?

j/k dont, its silicone powder

[Jer]

didja taste it?

j/k dont, its silicone powder

No and I'm pretty sure it doesn't taste like vanilla and chocolate.

[Grishbok]

One problem that affects the O2 sensor operation is contamination or poisoning by silicone, this shows up as a fine white powder on the tip of the sensor and will reduce the voltage output of the sensor when the mixture is rich, and this will cause a loss of fuel economy and increased CO and HC emissions. You may also see a negative voltage developed under lean operation when the sensor is poisoned by silicone. This poisoning causes the sensor to see a lower proportion of Oxygen.

from: SJMAutotechnik.com

[Jer]

Silicone poisoning of an O2 sensor? That's a new one on me.

[Grishbok]

I heard about it happening back when i was working on the rx7 I think, but its not something im familiar with... curious though, cus thats exactly what it looks like from your picture.

[jsigler2483]

OP- I would pull out your spark plugs and check those for a rich or lean condition. The O2 sensor is not an indication of either.