2001 Camry - Smells like burning rubber but is not smoking

After my Camry XLE V6 warms up to temp it starts to smell like burning rubber - my wife states that it smells like burnt popcorn. I bought the car and I believe it had been driven for quite some time with a bad upstream rear O2 sensor - when I hooked up my scan tool to it, it showed as a bad o2 and miss on #3 and #6 cylinders - I replaced the coil pack feeding #3 and #6 and runs smooth - put a Denso OEM o2 sensor on the rear and still has a miss code but not an emissions code - still smells like burning rubber - I figured the smell was coming from the bad o2 and it running bad AF mixtures. I figure that if the catalytic converter was plugged or needed replaced that I would get a code for it. I noticed a bit of oil around the valve cover gaskets so I gave them about a 10th of a turn down to see if it would stop the leak and steam cleaned the oil off the motor - still smells of burning rubber - car has never had the timing changed or drive belts for that matter. Drive belts look good, I will have them changed the next time serviced but I’m not sure about the timing belt…car has 218,000 miles but looks great - serviced regularly - bought from my dad and his cars last forever - any ideas about what this could be before I pay diagnostic fees for someone to look at my car???

Drive belts look good

Drive Belt???

If the car has 218K and has never had the timing belt replaced, it is living on borrowed time. I doubt that’s where your smell is coming from, but it is TIME.

"Drive belts look good

“Drive Belt???”

Some manufacturers use that term for the “serpentine belt” that drives stuff that the timing belt (or chain??) does not.

I will have drive belts replaced this next servicing, but i noticed on the block quite a bit of oil from the valve cover leaking in the front end…cleaned the oil off (most of it) and seems to smell a bit better, going to segrease the entire block and see what happens…this car is definately in need of servicing. Rear struts, valve cover gaskets, drive belts timing belt/water pump…its a good thing i know people to help me without a heavy bill.

“but i noticed on the block quite a bit of oil from the valve cover leaking in the front end”…
@JoSo–you found the problem. The oil leaking from the valve cover is dripping on the hot manifold. That will cause the odor you are smelling. If you open the hood when you get this odor, you will probably see smoke coming off the exhaust manifold. Years ago, I had a colleague complain about this burning rubber in a 1972 Oldsmobile. I went out and had her start the engine. As the car warmed up, I saw the smoke come off the exhaust manifold and then observed the oil seeping around the valve cover gasket and dripping onto the manifold.