sensors if there is no code. Can someone explain that to me? I hear people say that if there is no code that we should not change them. But how much of a difference do they make in gas mileage? I drive a lot and I want the best gas mileage I can get. What else can I do then?

 

I've had a rough idle, and new o2's were the cure.

 

Sometimes an O2 sensor (or any sensor) can go out of calibration and the computer will compensate for it slowly and not set a code (at least not right away) but the engine can run bad or hesitate because of it. The computer will know what is going on though, and it takes some scanner testing to see it for yourself. For example; if say the oxygen sensor swings in and out of it's normal calibrated range sometimes but not enough to set a code, the computer will know this and store it in it's memory. The data can then be retrieved through the scanner in mode 5 or 6 (a factory program used for the recording and testing/viewing of certain parameters during the operation of the engine). This is a very useful tidbit of info for those of you who have mode 5 & 6 access capabilities, but the info may not always be viewable depending on the year and model and of course it may be stored in "hexidecimal equations" . The info is stored as a % of failures and won't turn on the engine light until it has failed beyond a certain threshold a certain amount of times. The same is true for misfires. Does that make any sense to you? Any help at all? I don't fully understand it all yet, as there is so much info and it keeps changing year to year. Sorry if that's too much or too little info.

 

Most codes don't set until the system is a long way off. So a check on a plug in scanner once in a while to see if your well in range is a good thing.

 

Thanks guys, that really does help. I have a feeling that part of my gas mileage problem could be from bad o2 sensors. Any specific place I should purchase them from?

 

my next question would be why do some people take them off completely? What purpose do they serve? What happens if you have 1 off or all and can you pass inspection? Does it give you more power? Less gas mileage?

 

you cannot remove o2 sensors...period. you can however remove catalyst efficiency sensors somtimes called downstream 02 sensors which they are not. but a simulator will need to go in place of the sensor. ppl usually do this when removing catalytic converters.

 

How would I go about doing this?
I don't have any engine codes being thrown up but I wanna check the computer to make sure nothing is out of whack.

 

With MIL elims you DO NOT have to place the sensor in the pipe(only works on the post cat sensors) you can just wire tie it up out of the way. But If you replace them, replace them in pairs, they wear over time and if you replace just one, the PCM often "sees" the one not replaced as a failed one and sets a DTC.

 

Without a very high baud rate scanner or a VERY good o-scope it is not possible to watch the O2's effectively. If you have no DTC's then they are most likely fine. If it passes the KOEO and KOER tests, then everything that is PCM controlled or a input is up to "snuff".

 

Incorrect. The O2 sensor must be installed and must be functional in order for the MIL eliminator circuit to perform its job.

There is no need to replace O2 sensors in pairs if only one has failed. The PCM does NOT compare one side to the other, each bank is controlled separately.



Not really. A $200 hand-held scan tool or a $125 add-on for your laptop will work fine. The O2 switching rate is not particularly fast. The DLC communications rate is only around 10k baud.


Correct. Unless a fault code is present or the switching waveforms indicate the sensor is lazy or erratic, there is not point in changing it (them).

I'd start by cleaning the MAF sensor elements. It's easy to do and cheap. If the sensor is dirty, it will definitely cause fuel economy issues since the computer would not be able to properly computer fuel usage most efficiently. It will also cause driveability concerns such as stalling and stumbling.

If you do want to look at the PCM to see if its running significantly skewed from neutral, look at the long term fuel trim PIDs. It is desirable that both banks be as near zero as possible. When badly skewed, that is an indication that there is an imbalance that the PCM is correcting for a degraded condition. Once a LTFT reaches + or - 20%, you will usually get a DTC indicating a lean or rich (P017X) code

Steve

 

and one of the reason's ther is no schedule for 02 replacement -is that it is an emmissions device and ford would be responsible for that- increasing costs and affecting the botton line...

 

I'm going to have to get me a good scanner/tunner and the software one of these days. Just reading about it all the time isn't doing it for me anymore

 

Well then I guess everyone who has them tied up and out are working by some miracle. Look into them more, it doesn't matter the location.

Well I guess Ford told me wrong, I'm certified in All electrical and Engine Performance, and they DO compare the
O2's to each other. It is a function of the Emissions system, and catalyst monitor.





At a swichting rate of 5-7 cycles per second that is quiet fast. Can you count to 7 in one second. You can see the O2's on a cheap scan tool, but they are not accurate, you at most get two cycles per second on a fairly good tool. It takes a very good o-scope to get the CORRECT pattern, if you have ever seen a good pattern then you would know what I'm saying. Since we are picking apart each others posts!