Hi, I am hoping someone on here can help me with this! I have a 2006 Sonata. It has been at my dealers since last September. I have not had it back for more than 2 days at a time. It feels like it is misfiring, but not all the time. The trigger for this seems to be if I let off the gas and coast or ease off the accelerator, then when I accelerate again it jerks and lunges like it is misfiring. So far the dealer has done the following to no avail; changed the spark plugs (twice), carbon flush, new fuel pump, cleaned the throttle body & reflashed it. They changed the plugs for the 2nd time and gave it back to me on Friday. The same problem occured when I drove it home that night. I took it back in on Saturday and took the technician for a drive so he could see that it is still happening. Does anyone have any idea what this could be? They have checked everything on my car and can find nothing wrong, although they all concur that there is an issue here. They say it is NOT the fuel filter or throttle position sensor ( I asked specifically about these things). The engine light is not on and has never been on since I have owned the car. There are no codes on the engine. They put a sensor on my engine and had me press a button each time it happened that would show a diagnostic report to them, but it showed nothing abnormal. The technicins have all driven it and agree it is not right but have no idea what to do. They put a used engine in it in September after the engine failed (no compression) and I was able to provide all of my maintenance and oil change recepits. This started after the used engine was put it. HELP!! I am ready to pull my hair out, I want my car back! Any suggestions would be much appreciated!

 

First things first, what engine? 2.4L 4-cyl or the 3.3L V6?

 

Hi,
It has the 4 cylinder with 89,542 miles.

 

Does this engine have 89,542 miles or does the car have 89,542 miles? You said this was a replacement engine so I'm just trying to clarify. If the car has 89,542 miles, how many miles are on the replacement engine? Was it a new or used engine?

 

Oh sorry, should have specified that. The car has 89k, not sure how many miles on the engine installed in September, that was not disclosed to me. It is a used engine. I questioned it and was told that because it is thru my extended warranty they only authorize used, not rebuilt engines. (I bought the car from the dealer used with 20k miles on it).

 

Are you the original owner of the car ? Toasted engine under 10/100 would get a Hyndai engine in box.. extended warranty sounds like 2nd owner.

What was problem that first engine was bum.. need more than no compression.

Most respects, the 2.4 is an almost 95% trouble free engine, though I did replace 1 for hole in block (new in box complete engine from Hyundai), and a handfull of intake gaskets, and a handfull of oil control valves.

Sound like somebody just chasing their tails.. no codes ?? MIL ever illuminate ? Has to is something out of whack during 2 consecutive key cycle..

Push button, sound like they sent you on drive with flight recorder,, brown box with blue button plugged into power outlet and a large blue box also with black cable plugged into DLC under dash..

Sound like somebody to need to verify all connections as removed from previous engine out and used engine install..

 

I bought the car from this dealer with about 20k on it, so technically I am the 2nd owner. thats why the new engine went thru my extended warranty. I think they said the original engine had metal in the oil?? Threw a rod? The tecch told me he could tell I had maintained it well when he took the valve cover off. Of course the warranty company wanted all of my maintenace receipts, etc. Yeah I agree they are chasing tails here...guessing at what this is but evrything they have tried hasnt worked. Not sure what the MIL is? Yes they had a recorder that was supposed to record the problem and go back 10 mins prior so they could see what happened before the car started misfiring. They said it didnt record because it was too fast. I must have taken about 50 pictures for them in a 2 day period, but they got nothing out of it. I keep asking them if could have anything to do with the new engine and they keep telling me no. But that makes sense that a connection is out somewhere. It was really bad driving to work this morning...misfired probably 20 times in a 45 min drive. They are now calling in a Hyundai engineer to look at it. Hopefully that will help!

 

Heard from the dealer today...the Hyundai engineers think it is the transmission, so they are changing the transmission now.