Code 91, O2's again??? WTF???
 

&%$^$#&#*&!!!!
My Bosch O2's are only a year old. Has anybody had these things go bad in a relatively (i.e. 1-2 yrs) time?
What are the odds that both go out at about the same time?
Yep, the connections are good, clean, etc...
My Anderson PMS is confirming the lean readings, specifically .00 vdc for both.

Thanks in advance, and no, I still haven't put my wideband in yet...

Re: Code 91, O2's again??? WTF???
 

Few things to consider. (1) Don't try to do resistance tests to check for O2 health. You'll short the O2's out with the high impedence. (2) Common things will shorten their longevity....RTV, antifreeze, and leaded gas are just a few. (3) Poor grounding will increase the resistance of the heater circuit and kill them quicker. (4) Exhaust leaks near the reference source will lead to near zero voltages.

Re: Code 91, O2's again??? WTF???
 

Thanks Jeff.
I doubt I have an exhaust leak. At least not on both sides.
I'm cleaning connectors and will see.
Tomorrow I get my wideband installed.

Re: Code 91, O2's again??? WTF???
 

Update:
The car is running like crap. It starts fine, but smells rich. Then, after it warms up, it's like a light switch. The timing goes wacky (on the PMS screen it varies from 15-ish to 32 degrees at idle!) and the rpm drops to 550 and it backfires.
Sometimes, if I shut it off and start it again, it acts normally for a while, then the condition returns. My brand new 02's read .00vdc at idle. As you might guess, it drives poorly. Hesitation, etc.
I got my wideband 02 bung welded on today and will install the wideband tomorrow or Saturday. The only code is 91, 02's reading lean...
thanks for any tips...
Hozer

Re: Code 91, O2's again??? WTF???
 

Both the o2's should be switching realitively fast from lower numbers too higher voltage numbers...Make sure no grounds came loose or are coming loose...Check the EEC Ground bye the computer also that screws too the side floor of the kick panel...

Check EGR for smutt biuld up...Is that the only code... :confused:

Re: Code 91, O2's again??? WTF???
 

No EGR installed...I have that "EGR simulator" and as far as I know it's working.
Thanks

Re: Code 91, O2's again??? WTF???
 

I have found on MORE THAN one Ford product, that they don't seem to "like" the aftermarket sensors. Stick with genuine Ford replacement parts, and I bet you'll be OK.

Sounds kooky, I know. But I've seen it on literally dozens of cars/trucks at the shop I work at. :D

Re: Code 91, O2's again??? WTF???
 

I seem too agree with the Jester on using OEM Replacement parts..

Especially TP Sensors/IAC'S Etc...Had nothing but bad luck with the auto parts ones...

As far as the EGR Simulalor...I've never used one...If you think thats could be the problem..I'd put and EGR Plate back on and use the Original and see...or try plugging just the sensor itself back in and run a code check again after clearing the codes out of the EEC First and see if you getting a Switching from low/high Voltage signal from you O2's yet....JMO

gO BACK TOO SOME OF YOUR O2 Connectors and unplug them and plug them back in and maybe put some Electrical grease between the connectors and see if that does anything...If not write us back and well keep shooting at the problem... :D

Re: Code 91, O2's again??? WTF???
 

Update:
As I'm driving around today between work sites, the car is running fine. Perfect idle, good acceleration, etc. The 02's register voltage right away after startup. Typically, .02 -.06 volts within a few seconds and then they begin switching high to low (like .72, .68 back to .22, .34 etc)...
but what happens is out of the blue, while at a stoplight or something similar the 02's stop sending voltage. Or at least it shows up on my PMS as .00 on both 02's.
The car immediately runs like crap, the timing goes all over the place, the rpms drop to 630-ish at idle and it will backfire through the exhaust.
I've noticed the tachometer jitters erratically when this happens. So I'm leaning towards an electrical prob, not an exhaust leak.
Thanks for your input...

Re: Code 91, O2's again??? WTF???
 

Update:
I added some fuel on the PT table with my PMS and the 02's seem to be working better than ever.
By that I mean that around idle to 3k the voltages are hovering right around .46 vdc which is ideal.
It still looks to be lean up higher.
I'll finish installing the wideband tomorrow. That should tell the real story.