dbwade36

It was suggested that my 02 sensor should be considered for replacement. I believe it is the original sensor (almost 130k on the engine). I have no codes being thrown. But, I have had some issues with plugs, ( if any of you have read my recent posts). Question: should I go ahead & replace it? What exactly does it do? I meant to ask if Summit sells them, because I couldn't find it in their Magazine, but I will just call a rep @ Summit @ ask, unless someone knows the page #? yea?

[Modified by dbwade36, 7:22 PM 9/23/2003]


[Modified by dbwade36, 7:24 PM 9/23/2003]

Southern Comfort

Your car looks pretty good. A nice clean O2 sensor wouldnt hurt. :lol:

Lone Ranger

The O2 sensor reads the oxygen content in the exhaust gas and sets a voltage based on what it senses. The ECM reads the voltage and makes a decision on how to set the air/fuel mixture. Old oxygen sensors have been known to make the emgine run rich. In order for the ECM to set the fuel accurately it needs accurate data from the oxygen sensor(s). After 130,000 miles the accuracy oif your oxygen sensors is probably not optimal. Not off enough to set a code, but likely less accurate than it was 100,000 miles ago. They only cost like $40 and are usually easy to change.

Muffin

The O2 sensor is the keystone in fuel management. (OK experts I know there are a bunch of exceptions but I am trying to keep it simple) I just changed mine and it made a huge difference. I put in a Bosch which cost me $19.95 at a local parts store. At that price you can't go wrong.

dbwade36

Any pics of where the 02 sensor is located, exactly & how easy it is to replace? Do I need to put it up on a rack? Is it on the exhaust system? manifold?
Snap on type install? bolts, etc?

BlackRoseC4

Sometimes the O2 sensor is screwed into the headers. On a dual-cat system, check the O2 sensor, on the right cylinder bank, possibly just in front of the cats. Depending on the year model, it could be on the left side of engine, in exhaust pipe.




[Modified by BlackRoseC4, 8:49 PM 9/23/2003]

vader86

Well if your gas mileage is normal, then I dont think its necessary to really replace it. I dont recall what your resolution of the plug problem was, did all of them have that white tip on the electrode?

Normal mileage being 16-17 in town and 23-25 hwy, though your hwy mileage will be on the lower end of that because of the gears.

But if you want to replace it, its stuck into the exhaust in front of the precat, only sensor stuck in there, you cant miss it. Threaded in i believe, i've never replaced mine.

Jet-Jock

The long version: It begins with modes of operation, the ECM looks at voltages from several sensors to determine how much fuel to give the engine. Start mode, the ignition is turned to On the ECM energizes the fuel pump relay for 2 seconds to allow the fuel pump to build up pressure. The ECM checks the Engine Coolant Temp ECT Throttle Position TP, and Manifold Absolute Pressure MAP sensors to determine the proper air/fuel for starting. The ration ranges from 1.5:1 at -36°C (-33°F) to 14.7:1 at 94°C (201°F). The ECM determines the amount of fuel delivered in the start mode, by changing how long the injectors are energized. This is done by pulsing the injectors for very short times.
Run Mode: It has two modes open loop and closed loop. When the engine is first started and the engine speed is above 400 rpm the system goes into open loop mode. The ECM ignores the signal from the O2 sensors and calculates the air/fuel ration based on inputs from the ECT and MAP. It stays in open mode until the following are met: 1. The O2 sensors have varying voltage output, showing that they are hot enough to operating properly, 2. ECT sensor is above about 40°C (104°F), 3. specific amount of time has elapsed after starting. These conditions are different for each engine and are stored in PROM. When these values are reached the system goes to closed loop mode. In closed loop mode the ECM calculates air/fuel ratio (injector on time) based primarily on the signal from the O2 sensors. This allows the air/fuel ration to stay very close to 14.7:1.

Then all kinds of things are apply variables such as the IAC valve, TP position sensor, fuel metering, trim, pressure regulators and throttle body etc.

Basically an O2 sensor is a small variable battery. It has the ability to produce a low voltage signal that feeds information on engine exhaust oxygen content to the ECM.
Their operating temperaturs are 315°C (600°F). They are constructed of zirconia/platinum that conducts electricity under certain conditions. The platinum part actually stimulates further combustion at the surface which keeps the element up to the desired temperature. The inner cavity is filled with atmospheric reference air which is approx. 21% oxygen. The inner cavity is the positive terminal and the outer surface is the ground terminal. The oxygen concentration differences between the reference air and the exhaust gas produce small electrical voltages. Rich exhaust (more fuel) has almost no oxygen, while lean exhaust is about 2% oxygen or as it considers it excessive oxygen. When there is a large difference between the oxygen touching the inside and outside, it puts out like 600 mV while a smaller difference puts out signals below 300 mV. The optimum or reference is about 450 mV. This data is sent to the ECM which adjust fuel/air to run the engine.

Black carbon or soot can deposit on them from over-rich mixtures, but the carbon does not harm a sensor and can be removed by running the engine a part throttle or 2000 rpm for 2 minutes.

The RTV silicone gasket materials give off vapors that contaminate the O2 sensors. The sandlike silica from the RTV embed in the molecules of the sensor element and plug up the surface. The result is a lazy sensor response. You can tell it will have a white-like appearance. Some fuels contain silicone and those vapors too contaiminate them. Oil deposits will ultimately prevent the sensor from operating.

So without going into more detail, its very possible with that mileage they may be fine but just lazy from contaminants.

Replacing them will cause the engine to be much more responsive.


:seeya

dbwade36

I bought an 02 sensor & am going to put it in tmw after I get vette back from shop. (having valve covers installed.) Just to be safe. Heck, replaced everything else, why not. Was only $22 after military discount.

Jet-Jock

I may be incorrect but just for clarification, you did buy two correct? I believe there are two: Bank 1 and Bank 2.

Handle them very gently, no grease or dirt. Never drop them or handle it roughly. Never use any solvents to clean them. They use a special anit-seize compound made of liquid graphite and glass beads. The graphite burns away leaving the beads. P/N 5613695 for the anti-seize.

Torque 41 Nm or 30 lb ft.

Nathan Plemons

I think the early TPI cars only had one.

vader86

Just one on 86, on one side

Muffin

On the drivers side screwed into the lower part of the exhaust manifold. If you are having valve cover gaskets put on why not have the shop do the O2 sensor at the same time. It will take them less than five minutes.

redwing76

Jetjocky, are you the science guy or what? I went into a flat spin after the 1st paragraph. Information over load. My brain must be full.
Good post though.