Sante Fe 2004 with 4 Cylinder and automatic, 12000 miles. Timing belt has been replaced, both coil packs, plugs and wires have been replaced.

The issue, car normally runs fine. Steady speed, cruise on everything is normally ok. Then for some reason out of the blue it drops about 200 rpm and then picks right back up. This is intermittent and normally happens on rural winding hilly back roads. It's almost as if it can't find the right gear when it needs to. If I use the manual shift feature it rarely happens. Again this is an intermittent issue for which I have to explanation. Anyone heard of this? Is there a recall, or computer upgrade that needs to be done?

 

It's probably just the converter locking and unlocking as it needs more power on the hills. 200-rpm is nothing to worry about. Totally normal.

 

Might also be Throttle Position Sensor. I have a 2008 Santa Fe and had similar problem with rpms dropping a few hundred and also thought transmission was having trouble finding right gear. Dealer first reset adaptive values which helped for a few days before problem returned. Then Hyundai Teach support told dealer to replace transmission (only 36,000 miles) which they did, but problem remained. When I told service mgr about rpm drop they checked TPS, replaced, and I have had no problem for nearly two weeks! Runs/rides like a different vehicle!! Good luck.