I just recently bought upfront a used 2001 Volkswagen Jetta GLS Sedan 4D 2.0L I4 MPI with 134,XXX miles "AS IS" at a used car dealer on Monday 3/19/12.

FOR THE RECORD: I HAVE NEVER OWNED A VW CAR BEFORE

I checked the auto history with AutoCheck Report and so far the tittle is clean, odometer is checks out, however the most recent record on the report is on 09/2010. On the same day I bought the vehicle, I did a visual inspection which appear to be well maintained. There were no funny noises, no warnings signs or service lights on, car sounded smooth, and ran smoothly during the test drive. However, the car didn't pass the Smog Check because the dealer claimed that the car wasn't on for a long time. I took it home with no problem, no Check Engine light lit on.

3/20/12 Second day I owned the car, there was a slight very tiny bit hesitation when the car is accelerated and switched gears. Till this day, the car randomly does those hesitations, but it isn't bad were the car shakes completely, just a slight...almost unnoticeable. Unless that's normal on a automatic transmission.

3/22/12 Three days later, I go back to the dealer to get it smog, which is a 35 mile trip from my home, i notice that passing 40mph there is heat coming out the vents, unless that's normal, and the heater was not switched on. I check the car's temperature meter to see if the car was overheating, and so far the temperature was normal; the meter line was on the middle, that's why i question if its normal for VW car to push warm heat through the vents without having to turn on the heater. My windows were down during the drive if that has to do anything related to my discussion.

The dealer took the car to a shop to get a smog and wallah the car passed with no problem, but I wasn't there to see it because the shop was located somewhere else nearby.
On my way back home, 15 miles later, i notice the same heating issues with the vents and the service Check Engine light was lit. Yet, the car didn't make no hesitations, ran as normal.

Till this day the car drives normal, although it sounds like the engine needs oil which i will check later when the car is cooled off. My concern is if the Smog Check Test was legitimate or did the dealer disconnected the battery to erase the data from the computer chip on the day of the sale and did it again on the day the car got Smog. But if they did do it on the day of the Smog, wouldn't the Check Engine light would appear days later? I'm confused. As you can tell I'm inexperience car owner. Made a risky decision buying a used car paid in full.

What actions should I take? Take it to a reputable honest Repair Shop to fix the issue or not worth investing more money? I mean the car was purchased 'AS IS' yet the previous owner should be responsible following CA State regulations with smog test otherwise fix the issue. I have on paper that I bought the car on 3/19 and on the Bureau of Auto Repair website shows that on 3/19 the car failed the inspection. Then passed on 3/22.

Any suggestions?