Sabarrow

Have a 99 limited 4.0L and started having exhaust smell(rotten egg) Sometimes at idle its rough. Doesn't do it all the time and other than that runs great.

Snotzalot

Using Exxon? Exxon is known for rotten egg smell.

Radi

Is the CEL lit up? How old are the plugs and other tune-up items?
That smell can be sulfur in the fuel, a cat that's starting to fail, a cylinder dumping gas instead of firing, or an overly rich mixture among other things.

Sabarrow

Changed plugs, wires, air filter two weeks ago. Oil change and radiator flush a week ago. Just started out of the blue. No CEL light but bought used so pretty sure it's disconnected.

RTorrez1

Have it checked for any stored codes. Also just because you don't have the cel on doesn't mean you still don't have codes.

Snotzalot

You could have gotten a bad load of gas causing this and now you have a poisoned convertor. Run that tank out, fill elsewhere and then take it out and run it hard. You want the convertor to get hot to burn out the bad gas that has contaminated your convertor.

CCKen

Does the CHECK ENGINE light illuminate when you do a bulb check before starting the engine (Key to RUN/before cranking)?

CCKen

Suggest doing a vacuum gauge diagnostics to see if you have a clogged exhaust sytem (catalytic converter).

Rent a vacuum guage from your local auto parts store and plumb it into the unused vacuum nipple on the intake manifold then do the check in this link (senario 14).

http://www.secondchancegarage.com/public/186.cfm

Edit: Minimum vacuum at idle is 13 "/Hg.

Snotzalot

Using an old fashioned diagnostic method, how unique!