SHO has 4 o2's!

[Brett]

So my girlfriend was gonna get me some o2's for my bday. She called advanced auto, where the guy told her there 4 o2's.... 2 exhaust side and 2 intake side . Further more, they're only available through ford motor company, no part stores will carry it. She argued it but he was 100% sure. :laugh_ti:

Although i know hes not exactly on the ball, im still not sure the difference in description for the front and rear o2, so i dont know which ones to order, and dont want to end up with 2 of the same o2's. A couple say "upstream" so i know where they go, but dont know what one is for the back? Someone give me a hand please? :wave:

http://www.rockauto.com/catalog/x,carcode,1138799,parttype,5132

 

[Mr Anonymous]

sdpatt has posted the correct Bosch P/N's for the V6 O2's several times.

FWIW, most OBD2 cars do indeed have 4 O2's. The upstream (front) two monitor the A/F, and the downstream (rear) monitor the efficiency of the catalytic converters.

 

[dantheman68]

the back one is usually something like $2 more than the front... its wire is like 6" longer... i dont understand how that is $2, but it is


other than the wire, the O2s are exactly the same

 

[Phoenix]

If I remember correctly the rear ones are HEGOs , and those are heated.

At least that's what a Ford tech told me back in the day.

 

[Power Surge]

If I remember correctly the rear ones are HEGOs , and those are heated.

At least that's what a Ford tech told me back in the day.

They're all heated. The rears are there simply to check if the cats are working. The PCM looks at the voltage different between the upstream and downstream 02s.

 

[93rev2sev]

Is this right?.....

Heated mean that they don't work until hot(these are the upstream kind).

Downstream o2's are not referred to as heated.

 

[n8rsk8r]

the computer has a default setting (default a/f setting), think it is called a cold start loop..or something like that, then when the O2 is up to the correct temp the computer takes the reading off the O2.

edit:

Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.

A gasoline engine burns gasoline in the presence of oxygen (see How Car Engines Work for complete details). It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.

The oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.

The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.

When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

http://auto.howstuffworks.com/question257.htm


I just typed this outta the book "How to understand, service and modify Ford Fuel Injection and Electronic Engine Control"

The oxygen sensor is like a small battery. When it is hot, it generates a voltage signal based on the differential between the oxygen content of the exhaust gas, and the oxygen content of the ambient air.

The ceramic sensor body is a solid electrolyte and that generates a voltage only if the ambient air has a higher oxygen content than the exhaust The ceramic material must be hotter than about 300 degrees celicius (570 degrees F). On a cold engine it may take 90 to 120 seconds for an unheated oxygen sensor to get hot enough to start generating voltage.

In most 1988-93 EEC systems, and the beginning with 93' MECS, you'll find electrically-heated Oxygen sensors to improve emission control. During engine warm up, mixtures are rich because the system is operating open loop, not controlled closed-loop. The sooner the oxygen sensor becomes hot enough to send proper signals, the sooner the engine can operate closed loop for better control. A heated sensor may be hot enough after 10 to 15 seconds. V-type engines usually have two oxygen sensors, one for each bank.

Oxygen Sensor Operation

- Oxygen in the exhaust is a sign of a lean mixture because the exhaust has excess air-- air is left over after all the fuel is burned.

-Lack of oxygen in the exhaust is a sign of a rich mixture because all the oxygen is burned with the fuel--fuel is left over.

When the air-fuel mixture is lean, the exhaust gas has oxygen, about the same amount of oxygen as in the ambient air, so the oxygen sensor will generate less than 400mv. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in th exhaust than in the ambient air so voltage is generated between the two sides of the tip. The voltage is greater than 600mv. Remember rich = more voltage.

 

[Power Surge]

the computer has a default setting (default a/f setting), think it is called a cold start loop..or something like that, then when the O2 is up to the correct temp the computer takes the reading off the O2.

Yes, the computer runs in open loop (doesn't look at HEGOs) for a certain amount of time after startup. It's based off several things such as ECT and internal timers. This give the HEGOs ample time to get warmed up, so that they can be read when the PCM goes closed loop.

Upstream and downstreams are both heated. Older 3 wire cars from the late 80s used some non heated sensors.

 

[Mr Anonymous]

ALL SHOs use heated O2 sensors.

All MTX cars use 3-wire sensors and all automatics 93-99 use 4-wire sensors with separate returns for the signal and heater ckts.

Since nobody else can seem to find it using "bosch o2" as the search string, HERE is a link to a post by Scott P. with the O2 sensor part numbers for MTX and ATX. If your parts supplier doesn't carry Bosch, the numbers should cross.

 

[Mr95Gl]

FWIW, I used the (2) 13953's Bosch O2 sensors on my MTX.