Stalling and Power Problems

I have a 2000 Elantra which ran fine until recently. When driving it will lose power for a second or two and then continue. Also, when stopping or at idle it will stall. It's driving me crazy and Hyundai claims there is no recall so I'm posting before I hand it over to them or my regular mechanic for suggestions.
 
Thanks in advance for any replies!
 
BTW - No engine or other warning lights.
 
Thanks,
-B

Ok, well, it could be a number of things.. The idle air control IAC or could be a clogged Catalytic converter... When was the last tune up? How many miles on it?

Yep, couild be IAC, could be a throttle positon sensor or crankshaft position sensor, or.... it could be the ignition switch.  I haven't heard of switch problems on Hyundais but I had one go bad on my Escort and once it was fixed my stalling problem went away.

It has around 86,000 miles on it. The throttle position sensor was just replaced.
 
UPDATE: I have been running some tests over the last two weeks. I fueled up, added water remover solution and ran fine for a week. The next week I skipped the solution and just fueled up and had the stalling issues again. I just fueled up and added a higher grade solution to see how this week goes. Sounds like I might have a fuel issue (yuck!) but I will have to run this tank and see how things go. Not so fun

are you getting your fuel from the same station? Sometimes a particular gas station might have water in their tanks. I know they had a big problem about 6 months ago at a station here. I ended up not going to that station, seemed like every time i filled up, the gas sucked, so,  i stopped going there, and didn't have any problems since. Just a thought.