Hey guys im turning to you for help becuase guys on the probe forums cant really give me a simple straight answer to what my problem is. First check this thread to see what my problem is http://forums.probetalk.com/showthre...ighlight=P1169
what else could the problem be besides the 02 sensors that i already replaced? bad VAF?bad FPR?
The car runs fine and gas mileage is right about average (23 mpg around town).
any help wold be greatly appreciated.

 

According to Mazda shop manual for 97 626 with V6 engine the 1169 code is pointing to anoxygen sensorBank 1 Sensor 2 inversion problem. In other words, output signal remains above .45 volts for more than 42 seconds when engine rpm is greater than 1150 rpm and engine is at normal operating temperature. Looks like you got somewhat sidetracked on fpr. Do not know of any fuel pressure sensors on product that old but the fuel pressure regulator solenoid valve that controlsvaccumsupply to thepressure regulatorthat you checked and found to be ok would have set a P1250 so that sounds to be going in the wrong direction.
You have replaced all 4 O2 sensors so you know where they all are and you stated that you had an MIL eliminator installed for the cat efficiency code. This MIL eliminator is a device that would plug into the harness in place of an O2 sensor to send a phantom signal to PCM so cat efficiency codes would not be set yes??
According to what I see, there should be an O2 sensor located in each exhaust manifold about midway down. For ease of understanding lets call the sensor on right bank manifoldnear the firewall #1 and the sensor in left bankmanifold near the radiator#2. Heading on down the exhaust system the right and left side exhaust pipes join up to a single pipe. Shortly after this there should be another O2 sensor which we will call #3. Traveling further down the exhaust there is a cat converter and then the last O2 sensor which we will label #4.
My first question would be, Where have you installed the MIL eliminator?? #1, #2, #3, or #4 spot?

 

Thanks for the response, there is a on 02 sensor in each manifold, then there is an 02 sensor before and after the main cat (test pipe) which are bank 1 sensors 2 and3 which areafter the exhuast manifolds join into one pipe, i have the mil eliminator installed on the one after the main cat. which would be bank 1 sensor 3, so if the 1169 codemeans itsfor bank 1 sensor 2 that would be the 02 that would be the one before the main cat. That makes sense becuase the code doesnt pop up until i drive at a steady rpm (above 1500) for about a minute. So do i need to install a mil elimantor also on the bank 1 sensor 2 (02 sensor before the cat)?

 

So you have the simulator installed downstream of the main cat. I had thought that you had perhaps installed in front of the cat. Do not think that installing a simulator would work unless the simulation output voltage would be cycling voltage like a normal O2 sensor would be. What kind of output signal voltage does your other simulator create? If it is justa steady .45 mV then you would end up setting a P0140 code for O2S12 no activity.
Question is, why is theO2 sensor just ahead of the cat not operatingif it has been replaced already. An exhaust leak upstream of the O2 could be diluting down the exhaust with oxygen and creating that condition.

 

Yes its after the main cat, good thing you mentioned an exhuast leal becuase im pretty sure i have a very small exhuast leak somwhere between the exhuast manifolds and the main cat, when i step on the gas i can hear a faint hiss that gets slightlylouder with rpms. so that would make the pre-cat 02 sensor read to much oxygen and set the code your saying? what if i install a mil eliminator on the pre cat 02sensor as well?

 

An exhaust leak before an O2 will definitely cause the sensor to be giving a continuous lean voltage reading below .45 milivolts. The sensor is simply responding to oxygen content in the exhaust gases and is not able to distinguish between unburnt oxygen left over from combustion and oxygen that has leaked in from a gasket or crack in exhaust. Do not know if simulator would work in place of the upstream O2 as it is primarily designed to be installed after the cat. Would not think it to be a good idea as the engine computer still uses this signal to some degree to determine overall fuel correction needs.

 

Hmm several people have told me that the pre and post cat 02 sensors on the 97 (only 97 as 96 has all 4 02 sensors mounted in the exhuast manifolds) are used ONLY for emissions purposes and will not effect performance and that might be true becuase even with the code the car still runs fine and gets the right gas mileage. If i cant find the exhuast leak and am forced to try installing a mil eliminator on the pre-cat 02 sensor which one do you think would be better the spark plug defouler type or the one were you wire it into the 02 sensor wiring.

 

Not very familiar with either. Just needs to have an output signal voltage that would modulate back and forth over the .45mV point so computer will not then throw a no activity code.

 

OK, did some further research and found out by monitoring my 02 sensor voltages while i drive that the pre cat 02 sensor doesnt put out any voltage most of the time and sometimes it puts out a little (.015-.050) and sometimes it puts out the normal amount (.4-.7) All 4 02 sensors are new, and i also tested it according to kevins post (with a volt meter hooked up and using a torch to heat up the 02 sensor), and it passed the test with flying colors. Now my question is would a small exhuast leak cause the voltages to go like that? and if so why doesnt the 02 sensor after the cat (test pipe) also respond like that.

 

War97GTS, to be frank I am not very experienced in this matter but would like to say what I think. As far as I know if both O2 sensor and the engine are OK the sensor shall put out voltage which continuously floats from 0.1 to 0.9 V (it is better to use a needle voltmeter and not digital).

If the voltage does not float at all (for instance, always stays 0.2 V) or floats but out of the above range then there are usually only two reasons of that:

- O2 sensor is defective, or
- There is a problem within the engine.

As to the engine’s problems which can cause O2 sensor wrong output it could be either false air entry or low fuel pressure. Since you already replaced all your O2 sensors you may want to have a look at the engine…