pmnuon79

hello, new to the forum. purchased a 2006 is350 about a month ago with 70k mi. have been noticing a fartsy kinda smell under hard acceleration, but would taper off about a minute later. it only happens after ive been driving around for about 5-10 min, then any kind of hard acceleration it happens. I've searched around the these forums, the cat converter or battery may be the culprit. no cel on so far. my mechanic of 20 yrs checked my cat and exhaust, said they were normal, no leaks in the exhaust. brought it to the lexus dealership but they couldnt recreate the smell. What i did not find in the forums is why im here asking for your help....at first the smell would occur with the ac on or off. but about two weeks ago this started happening, with the ac on, no smell whatsoever while accelerating hard. however with the ac off, the smell comes back when i gas it. any help would be much appreciated. my knowledge on cars is limited, not sure why it doesn't smell with the ac on.
thanks in advance

MEAHT

iTrader: (1)

it might not be this, but its worth checking to see if your battery is going bad. You never know.

ISland350

Sorry have no idea either, but one of THE best thread titles in a while!

asuraIS250

iTrader: (1)

I had a similar problem when I purchased my IS, it was the battery for me, I suggest pooping your hood and have someone turn your IS on and see if the smell is coming from the battery, I'm pretty sure your going to need a new battery, I would suggest going with a gel cell battery like optima

idoke1

iTrader: (5)

Check your cabin air filter.

Sffd103

iTrader: (16)

Try changing your cabin filter or your diet. Lol

ISland350

pmnuon79

Thanks for the input, I'll change the battery first

Ants350

iTrader: (1)

I try cabin air filter first .

my1s250

iTrader: (1)

maybe its the mildew buildup in you vent.....

embolism

don't accelerate hard!

Gville350

iTrader: (10)

The smell is normal, it is the four cats doing their job and when you smell this you know they're working. This happens all of the time to me, only during the first or second HARD accel during my daily commute (w/ or w/o the A/C on)...which happens every day cuz of love my IS350!

Raybean

iTrader: (3)

Not normal. Failing cats has a rotten egg smell.

pmnuon79

would failing cats make the check engine light come on? it hasnt yet...

FSportIS

iTrader: (13)

Did you have the AC "Circulation outside mode" on? If yo did, outside air would comes in and comes in strong when you accelerate hard. Just put the AC "Circulation inside mode" on and you won't notice the smell.

Change your AC cabin filter with the De-odorization version as well.

AC usually smells a bit when first turn on, i notice this in many cars but it seems weird that the smell goes away when AC on in your case lol.