samco hoses = contaminated o2 sensor?

Brett Dikeman brett at
Wed Oct 6 23:17:06 EDT 2004

At 5:36 PM -0700 10/5/04, CL Wong wrote:

>Pulled the sensor with my 22mm crowsfoot wrench found
>the tip to have a uniform whitish/greyish coating on
>it.... hmmmm

That's completely normal after 60k.  The sensors, however, do not 
last much beyond 60k, and the Bentley advises outright replacement on 
the 20vt after 50k if the sensor is even suspected of being 
defective.  Any oil consumption will reduce life drastically, as will 
overfilling the engine (hence the big red sticker on the t-belt 
cover; folks, you fill to half-way between min+max, not "to the max 

   The only way to really tell if the sensor is toast is to look at 
the ECU's adaptation values (this test needs to be done under a 
specific temperature/operating time), or put a tracing scope on the 
O2 sensor output and see how fast the sensor swings as the ECU 
balances mixture for the 3-way cats; the sensors "slow" as they age 
(which can lead to premature cat failure if let go too long; the cat 
gets "loaded" too much in one direction from stoich, then too much 
the other way; that causes the cat to run outside its design 
temperature range).

>Preliminary mileage seems to show a 1-2mpg improvement
>over my 90 mile-a-day highway commute.  Looks like it
>will settle at 23.5 after a few more days of driving.
>(was getting 22mpg with my right foot in economy mode)

There are too many factors to make this "proof".  Among other things, 
the ECU was adapting to the new sensor.  Weather(colder = more 
power).  Traffic(was average speed identical both trips?)  Your own 
foot.  People are convinced that changing X did something do their 
mileage because the trip computer shows a reading .5 to 1 mpg higher. 
It's simply not true; it's you driving lighter because you're more 
conscious of fuel economy.

What does this have to do with samco hoses?  The notion that silicone 
rubber caused the sensor to fail?  Silicone SPRAYS, lubricants, etc- 
those will most certainly cause sensor problems.  Silicone rubber 
will most certainly not, unless the car has been ingesting pieces of 
the hose...

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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