Bad Oxygen sensors ?
 

My check engine light came on and my truck will not idle when you come to a stop and you let off the gas it will die. So I took it Auto Zone and them check it.
They told me it was my Oxygen sensors and I needed to replace them so
I purchased the two front sensors like they said. I replaced them and reset the computer but it did not seem to make any difference. The next day my check engine light came on again. So I took it back to Auto Zone the next day and them check it again . They said it was the front side oxygen sensors again that I need to bring them back and get new ones. So I uninstalled them and took them back and got new ones and installed them. The next day my truck ran about 20 min. and then the check engine light came back on. So I took it back to Auto Zone and guess what, the code said it was the oxygen sensors again and I need to replace again. I told them this was the second pair in three days could it be something else. They said they did not know. I can't believe these sensors are going out. Has to be something else wrong? any help would be greatly appreciated.

Thanks,

Sounds like the IAC (Idle Air Controller) to me. Look up other posts on this and see if it doesn't sound right.

If you post the codes that AZ is reading then others on here could confirm.

This sounds like exactly what happened to me except I didn't fall for that "bad oxygen sensor" crap (no offense). Auto zone (my local store) read my OBDII code the told me the computer was showing code(s) for a lean mixture on both sides which was most likely caused by, not one, but two oxygen sensors going bad at exactly the same time. Ya right! So after doing some research on the codes including this forum I set about looking for a vacuum leak. Makes sense right? (lean fuel mixture). I ended up finding a hose connected to the back of the intake plenum which had a pretty big hole in it. If I remember correctly it went to the PCV valve. Any way, with the engine running you can usually hear the larger vacuum leaks.
The point of my long winded reply is this - The sensors are there to warn you when something is not right - trust them.

One more piece of advice if I may....Take the new O2 sensors back, install your old ones, and invest the money towards an OBDII code reader.

Same thing happened to me. I replaced all 3 o2 sensors for a total of around $ 200.00 and still have light and same codes. It shows the sensors near engine on both sides. Heater circuit.

I'll try also to find a vacum leak.

The hose that went bad for me was a little 3" 'L' shaped hose directly off the back of the intake. You wont hardly be able to see it the way Ford tucked the motor in under the fire wall. With it running reach back there and feel around. If theres a leak you'll be able to feel it and hear the tone change when you put your finger over it.
I'm telling you this because I've heard other people have the same hose go bad.
The good news is this hose only cost about $8 at Ford.
Good luck.
John

And this is why we get Autozone to check codes but not to suggest what needs to be replaced ;)

And Hi Bolan, welcome to the forum :)

A dirty MAF can also cause O2 codes.

jllillie, Thanks I'll check that hose out.

Racerguy, what is the MAF?

MAF = Mass Air Flow sensor.
If you look in the "frequently asked questions" at the top of the forum you'll find instructions there on how to clean it.
Let us know how it goes.

I replaced the vacuum connector on my Crown Vic yesterday, it took 15 minutes...and smoothed the idle. :-X10

Thanks, for the help. Turns out its like you said, it was a vacum leak in a little L shape hose that came from the pvc valve and connected under the injector. If I had not cut the wires on my old sensors to get a boxed in wrench on them I would take them back to Auto Zone for a refund.

Thanks again for all the info

A small price to pay, just figure how much it would have cost you if you went to the dealer and you will feel better. Glad you go er fixed.