I as well have 03 g35 4door sedan and my car has been having the rubber burn smell on march 02 and my service engine soon light was on, so I looked under my car and I seen my o2 sensor connectors were broken. so I thought that was my problem, I replaced my sensor and my service engine soon light went off just yesterday. but I still smell the burn rubber, I don't push my car hard, I always go with California speed limit. any help on what it is :/ when I was under my car changing the sensor I noticed I had a leak,,,,,could it be burning oil.....

 

ah, the infamous burning rubber smell. Have the same problem on my 2005 RWD sedan. I've learned to live with it every winter because it has happened since I bought the car with 19K miles. The ONLY time I will get the burning smell is with a combination of the three - running the heat, roads are wet/snowy and I am stopped for over 30 seconds. It will fill the cabin with a nasty burning rubber odor, unless I kill the heat or start moving. Recirculating air helps too. Passengers unfamiliar will the smell will ask me if my car is on fire .

Have never found the source, but since it only happens when its wet outside, my best guess is a belt slipping. I've changed my belts twice and tension is within spec.

 

I'm actually starting to think it's the belt slipping a bit.

Just this AM, had to pass a prius so i floored it. Engine went WOT, i heard a small bit of belt screech for a second, and then a few seconds later I got the burning rubber smell in the cabin.

Looking around in my engine bay, belt is def due to be replaced, but one of the idle pulleys looks like it's had some slippage on on. Might have to check to see if it's starting to become stiff to turn?

Good thing spring is coming...i need to do some routine maintainence. Pretty sure a rear caliper is seized again, my front wheel bearing needs to be replaced, and need to do usual fluids.

 

I'm in the same boat as you. Belts are due to be replaced, along with all fluids. I had to change the left rear caliper yesterday - lots of fun in the rain LOL. At least it wasn't freezing cold though. My right rear caliper seized up two winters ago at 73K miles, this one made it to 92K. What a crap design though, that you need to swap the entire bracket. It could have been a 5-minute job if they just rotated the caliper up 2".

 

My thoughts exactly. If they rotated it up 2" or so they probably wouldnt get so much exposure to moisture and the lower pin wouldn't seize up.

I replaced the driver's one 2 years ago, and 99% sure the passenger one is seized up now as my pedal is soft, and i can hear the rotor scraping lightly all the time back there (plenty of pad material)

If only i could find a vendor that sold the brackets only instead of having to order an entire caliper (and then swapping the caliper because I can't not use a new caliper vs leaving the original rusted one)

 

Mine have actually had the pistons freeze up solid - I couldn't even compress them. Not sure what got in there; probably rock salt and other trash that rusted the piston in place. Very frustrating!

 

Pulled the brake apart last night. FOund it wasn't seized, but both rear calipers had worn the pads down as far as possible before the backing plates would start to make contact. Threw it back together and ordered some Akebono pads from Rockauto. Figure i won't drive it this week to save my rear rotors from damage.

On a down note...discovered both front wheel bearings are junk....again.

I'd ditch the car, but two bearings, new belt and idlier pullies, and rear pads is still cheaper than a car payment.

 

In addition to the smell, I've had the dreadful engine tap come up in the last month.

Eh...so I had 2 mechanics check it out.

One said the cat.

One said its coming from the engine.

I'm more inclined to believe its the engine. I'm getting a engine check later this week.

No CEL light yet, and no noticeable loss in performance...but ive had issues with burning oil and leaking oil that I thought were resolved, and i think this is just the chickens coming home to roost...