Hyundai Repair: 2002 2WD Santa Fe - noise and vibration, crankshaft sensor, excessive vibration

Question
Hi I just had my Santa Fe (75,500miles) towed to a shop after it quit on me while driving.  Apparently the crankshaft sensor needed replaced.   While at the shop, I also replaced the timing belt, idle belt and front brakes.  When I picked up the car it was driving heavy - and was really noisy.  Seemed as if it was revving higher with out shifting itself. But I was told it was shifting fine.  And it now  seems to have a vibration in the gas petal and dash. I am really bummed - I used to love my car, now it is no fun to drive!   I am wondering if it the flex pipe vibrating and if so, will this cause a lot of damage if I don't fix it?

Answer
Hi, Jodie.  I'm sorry it's been so long for you to receive an answer.  It appears that a previous expert left and the questions he didn't answer were simply dumped into the system.  I didn't check here very frequently because the questions all appeared to be at least six months old.  Now, I'm trying to whittle them down little by little along with my other questions.  If you are still having the issue and need more information than I've provided, please follow-up with me.

Presuming you have the 2.4 liter four cylinder, my instinct is that the front balance shaft may have been timed incorrectly.  Because of the way the balance shaft is driven by the sprocket, lining up the timing marks doesn't necessarily guarantee that the shaft is properly timed.  Usually, this results in a high-frequency vibration that increases in intensity as the engine is revved and is about four times the engine rpm.  Chances of significant damage are small, but excessive vibration can cause fatigue on a number of components.  If my suspicion is correct, there's little reason why the shop that replaced the timing belt shouldn't be able to repair it at no charge to you (since they would have installed the timing belt incorrectly in the first place).