About a month ago I got a cel for both primary O2 sensors. I replaced both of them and the engine light still comes back. I thought it may be a fuel issues and even swapped out the fuel regulator with a spare I had lying around.

Not sure what else can trigger a false reading. I got the warranty from Autozone and my change them again.

Any suggestions. Car has 230k miles now.

 

What's the code say?
O2 codes don't necessarily mean the o2 is bad. You could have an fuel trim issue, vacuum leak, injector issue, spark issue etc...

 

Its only 0303 and 0503. I too think it can be something else. The car has been idling a lot rougher since the code first showed up. Was reading yesterday it can be a bad coil pack. But I don't have any misfire engine codes.

I have 3 spare coils sitting around so I may do some trial and error. Don't want to break apart the fuel rail yet.

 

Clean your egr tube and is your car cali or fed spec?? If its cali spec and your o2 codes return after installing new o2 chances are your precats are bad.... My 5th gen has all new o2 installed and it turned out i had a bad precat on the car... 300 dollar job or so if you do it yourself... If you are fed spec you shouldnt have precats so id start with cleaning egr and iacv also check for damaged or cracked vac lines replace as needed...

 

good advice above me, however...

Fed spec maximas have the same pre-cats that Cali-spec ones do. The difference, is the Cali spec maxima has one O2 sensor before AND after each pre-cat, and none after the main cat. Fed spec have one before each precat, NONE after each precat, and ONE after the main.

 

Got a y-pipe, 00VI setup, don't even have an iacv.

Cleaned TB, EGR is a non issue given 00VI.

I took the plug out from each coil pack and each time there was a noticable change in idle. I didn't replace any coil packs yet. And I may end up changing the plugs. I know I have something like 15 or 20k miles left until they need to be changed.