I have a 1999 Malibu and I've been having some issues with it for awhile. First off, my AC controls 3, 4 and 5 are the only speeds that blow out any air, the others (1&2) don't blow any air unless I'm going down the highway. With that said, lately I've noticed that when I am going down the highway, and I have the AC on, my car acts like it wants to stall; it sputters sometimes and when I try to give it gas it acts like it doesn't want to go. Also, if I am going down the highway and the cruise is set, I will sometimes feel a slight jerk and the cruise control will shut off. I'm afraid this could lead to further problems and I only have 3,000 miles left on my warranty. I like to post to forums before I take it into the shop and pay someone to look at it. Sometimes taking it in doesn't do anything but rack up a big bill for nothing.

Any help would be greatly appreciated!

There is a thread that talks about the fan issue. A $20 part should fix it. Look at this link:
http://www.automotiveforums.com/vbulletin/showthread.php?t=324040

I'll take a stab at the other issue. I would take a look at:

Fuel pump
Fuel filter
Oxygen sensor (even if there are no codes)
Ignition coils

Good luck.