99 4runner 3.4 a/t 4x4. i was wondering if my rear o2 sensor is out i start up in and it sputters for a second and after that its fine but when its hot(weather) its starts doing it again at a stop i have 1 cat a front o2 and a rear o2 i replaced maf and did isr mod(correctly) i do smell a rich sulfur smell out the back when driving with back window down i did have a new muffler installed since old one spider cracked at the pipe(flowmaster 40 with 3 inch turndown) i do have cel azone said faulty catalyst idk is cat or o2 sensors

 

Front sensor is the O2. Rear is to check the condition of the catalytic converter.

 

ok cool so what should i do? ive had it checked at azone but everyone said possible bad cat but sine it only has 130k onit i highly doubt if cat more of a sensor issue correct?

 

I'm sure it's not a trick question. Get the cat tested, if it's bad replace it. Simple

 

the cat does look like it has been replaced though.

 

OK, quit asking for advice if you aren't going to listen to it. There's no possible way you can tell the condition of a cat by looking at it.

 

The sulfur smell is because it is running rich. That is NOT the fault of the cat. It could be the O2 sensor (front one only), MAF sensor or something else. HOWEVER, if allowed to continue for any length of time, running rich WILL KILL your cat and you will have a dead cat PLUS whatever problem caused the issue in the first place.

It could even be that your PO replaced the cat because of this problem, and didn't fix the underlying cause. Cats rarely die on their own--they are killed by physical damage or by a poorly maintained engine.

How's your fuel mileage? Even money it sucks....

First, I would scan again and post up the actual numeric P-codes for us to look at and not rely on the no-brains at AZ to interpret them. I personally have no advice for you until I know the actual codes being thrown.

 

what the end result was my intake had a leak after the maf. fixed for temp with a crap load of elec tape wrapped around the elbow at the t.b