I have a '98 Toyota 4Runner 4WD. On long drives or those with hills, my truck makes a sulfur-like smell, almost like burning oil? It doesn’t seem to be affecting engine temperature and has been going on randomly for about 8 months. Any ideas?
I suspect you are smelling a bit of hydrogen sulfide gas (H2S) coming out the exhaust. The fact that you mentioned hill climbing suggests this diagnosis.
If this happened only one time I would suggest you picked up a tankful of bad gas, one that had too much sulfur content. Since it recurs we consider a malfunction somewhere.
Some folks would quickly accuse the cat converter and they may be right. But this can be the result of an engine running too rich. I would start by giving your vehicle a basic tuneup, plugs and air filter, and see if there’s a difference.