info about 02 sensors please

[Perry Mitchell]

Can someone advise me regarding the 02 sensors? I read somewhere on this forum that the end of the sensors, where the wires exit, needs to be clear of any covering. I don't remember why but the reason I ask is because I covered the wires with approximately 6'' of heat resistant material because one of them is close to the transmission pan. Yes, it is an automatic that I have in my '67 Camaro with an LT5 transplant. It also has long tube headers. Could this be the reason it runs very rich?

[Karl]

I have heat shield wrap around both of my o2 sensors wires and I have headers. My last Dyno run I was lean.

I am guessing you need some "tuning" to your chip to lean it out some.

[XfireZ51]

Not sure about why its running rich, but the O2 sensors basically compare the O2 from “free” air which is supplied by the exposure of the end of the sensor w what is coming out of the exhaust. So I guess I would expose the end and see what happens if anything.

[Young1]

The issue you speak of is sealing the individual wires with silicone where it enters the sensor. The larger than the wire diameter of the hole allows the sensor to equalize itself with temp changes. A heat resistant covering for the wires will cause no issues.

[Paul Workman]

Speaking from personal experience, closing off the air (i.e., sealing the entry point of the wires [with RTV, in my case]) caused havoc (rich) until the O2s were replaced WITHOUT the RTV.
The O2 wires are made to resist high heat from close by exhaust pipes. The proximity to the trans pan doesn't come close, heat wise.
Protect the wires if you feel you must. But, leave the point of entry open to the air. That issue removed, the A/F ratio will correct itself, unless there is another issue.

.

[Perry Mitchell]

Thanks to those who replied. I am still confused because I do not see where the wire end of the sensor can ''breath''. The wires enter the sensor through a plastic plug that has individual holes with a tight fit for each wire. I installed a covering over the wires using shrink wrap around the upper metal portion of the sensor to hold it in place.

[XfireZ51]

The FSM explains how it works.

[Paul Workman]

Originally Posted by Perry Mitchell

Thanks to those who replied. I am still confused because I do not see where the wire end of the sensor can ''breath''. The wires enter the sensor through a plastic plug that has individual holes with a tight fit for each wire. I installed a covering over the wires using shrink wrap around the upper metal portion of the sensor to hold it in place.

Be that (above) as it may, the O2s work with a sample of ambient air...that's a fact.

Maybe the wires are not tightly held (sealed) by the entry "plug" or there is another vent somewhere, IDK. (There is very little room for air flow on any O2s I've seen, BTW.)

So, take it for what it's worth: it made ALL THE DIFFERENCE in my case. I suggest you leave off the shrink tube from the entry point and see what happens!

[Perry Mitchell]

Thanks Paul. Removing the heat shrink is the first thing I will do.

[Hib Halverson]

O2Ses need a source of "reference" air. They get that through the sensor harness.

If the sensor is a good quality unit (ie: Bosch or Denso) and the harness is routed properly you usually do not need extra thermal protection but, if you want to add some temperature protection, don't use anything that "shrinks" in place or fits tightly. Use a thermal insulating "sleeve" that is open on both ends. MSD Ignition sells stuff like that. Disassemble the WeatherPac connector at the end of the sensor harness, slip the sheath over the wires, then replace the connector.