These have very likely been covered before, but here goes:
I’ve got a 2006 Hyundai Sonata (6-cylinder) I bought used, which other than abysmal gas mileage (other than that, Mrs. Lincoln…), I like very much. However, there are a couple things I haven’t found out about yet.
1. The transmission seems to be acting as a brake in low gear - there’s a definite resistance, even while accelerating, which disappears when it either shifts up, or I take it out of D. Is this some bizarre design feature, or a sign of a problem that I didn’t pick up when checking it out? Any guesses?
and 2. There’s a foul smell that comes and goes - rather old-cabbage in nature, but it disappears when the car has been baking in the hot, hot sun for a bit. It’s strongest after a cool, damp night, and I suspect it’s mold in the vents/AC somewhere, but any plausible guesses (and suggestions) would be welcome. I’m hoping it’s not associated with the suspicious brownish stains splashed over the upholstery on the front seats…
I can’t answer (1) without actually testing your car myself. Maybe it’s merely your perception, maybe there really is a problem.
As for (2), this is common. You do have unwanted growth in the A/C box. Likely its outlet is clogged and the box is accumulating water and debris. You smell the growing mold. Unclog the outlet, a short open rubber tube probably extending through the bulkhead into the engine compartment. Use a stiff wire. The mechanics do it by blowing compressed air into the tube. Then clean up by spraying copious amounts of Lysol or equivalent into the fresh air intake, usually located under the cowl area.
Thanks! I’m now thoroughly intimidated upon opening the hood of these modern engines, but I should be able to manage that.
About the smell, the first thing you need to do is determine if it is coming from the AC system somewhere in the cabin for sure rather than just guessing about it. It should be pretty easy to do. Is the smell stronger when you get into the car before you start it and diminish after you start it and turn on the blower, or does it get stronger when you turn on the blower. Is it stronger when you stick your nose in front of the HVAC outlets?