Hi there! I have some strange problems with my 92,000 mi 2000 GL 2.4 4-cyl manual Sonata -- a few weeks ago I had the engine block replaced & valve job done under warranty (car burned oil from day 1). Soon after getting the car back, it started having major problems with hesitation. You would be cruising along and then all of a sudden, the engine power would drop significantly, then if you pressed the gas or you did nothing and a few seconds went by, the power would kick back up. No warning lights went on. The problem disappeared in a few days. When I took the car back to the dealer, they said there were no problems found and no codes. They said no TSBs they knew of. A week or so after that, the battery died. It was several years old. I had the car jump started and I left it at my parents before I left to go out of town. AAA came and diagnosed a bad cell in the Hyundai Interstate battery. So I picked up a new battery at Sams Club before coming home when I then installed it. The same thing started -- you would get hit with these hesitation "events." over and over while driving. Then, a few days later, it stopped and the car ran fine. THEN.... I took the temporary battery back once I was able to get a new battery of the proper size (Hyundais take an odd size battery model that has a lip for a retaining bracket....). The people who put in that new battery said the alternator was giving normal output readings. Lo and behold, after I left the shop and for a few days after, the same thing happened with the hesitation. It has since gone away. The engine now runs beautifully, better than it ever has, and the idle is finally glass-smooth.

Does anyone have a clue as to what may be going on with this problem? I'm not even going to speculate.

Also, one more little thing -- a few days ago the dashboard "trunk open" light started flickering on and is now stuck on -- unless when I'm accelerating, then it goes off. Any ideas?

:3gears:

This is one suggestion on this generation of sonatas. Sounds like yhou have a misfire in one of the cylinders (hesitation problem) then lack of horse power (which is the 4th cylinder not firing right). The way I took care of this problem was to spray water and baby soap on the engine bay and noticed sparks from the 3rd cylinder. The solution was new spark plugs and a coil pack and things were fine. Also this problem if it does not happen constantly and kicks in and out will not deliver a code. That is just the type of computer system we inherited by buying this car. Hope this helps.