Rough/Loping Idle, Hesitation, Sulfur Smell

[Noobz347]

My mustang is do the same lopey idle. But I just noticed it so it may just be the coil, will find out later today.
I am wondering if anyone on this topic who smelled the sulfur has actually checked their catalytic converters?
While driving my car I have never smelled it, however, there has been two or three different instances where I smelled that smell- but only while I was a passenger in my car, never while driving it. And the smell is not consistent.
Would a faulty 02 sensor cause the cat to fail?

(I am newISH to the whole mechanic thing, so forgive me if I sound like I don't know what I am talking about! Chances are if I am asking, its cause I don't. lol)

If you had a faulty O2 sensor, your Trouble LIght would be illuminated on the dash-board.

It is not uncommon to get a sulfur smell from catalytic converters, even when they are in perfect working order.

It not uncommon to get a sulfur smell from the catalytic converters of the vehicles driving ahead of you either.

The above items out of the way, I have a hunch that you have a vacuum leak somewhere and that it's a rather small one.

 

[PaulKennedy]

A while back my car developed a small hesitation in the low-mid range cruising RPMs.. it would buck a little while cruising at 2000 and so I'd downshift and it was fine. Well, the problem seems to have developed further and now I have the following:

rough and lopey idle.. sounds and feels like I have a huge cam, definitely not VT stage 1; my exhaust note is also much more lopey throughout the entire range
stumbling on acceleration and i still have the hesitation at cruising
just recently I've started smelling a burning in my exhaust, smells kind of like the sulfur from fireworks
faint ticking/tapping in my exhaust note, as well.. though I can't hear this all the time

now, the idle is lopey/bad enough that to ease the car forward in first gear, i have to rev it up to about 2000 rpms to let the clutch out or else it'll jerk and buck out of control. if i try to launch relatively quickly, the RPMs will dip to around 1000 and the car will sputter and choke until i stab the throttle and the engine gets back up to speed. also, the lopiness is experienced at startup and can sometimes make it start up fairly rough.

what i'm considering so far is the EGR valve, something with the ignition or (hopefully not) something internal, maybe a piston, i dunno.

any help or suggestions would be greatly appreciated.

I just had this problem, i know im a bit late but for anyone recently having problem i changed my fuel filter and that did the trick for my 01 gt