Howdy,
I'm a brand-new member here and new Hyundai user / mechanic / critic. I'm a pretty good mechanic of necessity, an engineer by trade and as such, a staunch critic of every engineer who's ever designed any component of any vehicle ever contrived on this planet (and maybe even Mars).

I'd never had much to do with Hyundais, other than borrowing a Santa Fe once and thinking it got over twice the mileage of my Grand Cherokee. Also, my sister's family had two Sonatas and loved them. A month or so ago, my sister bought a new car and offered her '09 Sonata GLS V-6 to my son for a good price. She'd loved it and the only major problem came from her backing over a barricade. It seemed like a great car! We liked it so much that when we found another, ('06 GLS I-4) we bought it for my daughter with the added bonus it came with an extra set of wheels and brand-new winter tires (badly needed on the V-6).

But then came the problems, complaints and cussing. The alternator failed in the V-6 just when we bought the I-4. We let the I-4 sit over the weekend to get insurance and registration and went to work on the V-6 alternator and, while in the garage, decided to swap out the wheels and tires as well. Although the wheels were smaller, they look good and it was an easy changeover (we thought ...). Long story short (or is that short story long?) both jobs were nightmares! We stripped a stud on the LF hub and spent hours fixing it, while cussing out the idiotic Korean design of the hub / bearing set up. I can do the same job on my F-350 Powerstroke in a half hour. The alternator was even worse. An easy job made nearly impossible by thoughtless, stupid and senseless placement of hoses, brackets, A/C plumbing etc. If you've ever changed one out, you know what I mean. Again, the same job on the Powerstroke takes about 15 minutes. (In all fairness, I'm always cussing out the Ford engineers too ... somehow, cussing out engineers makes a repair job far more satisfying.)

We got the V-6 back on the road and got the I-4 registered but noticed a lot of noise in the front suspension (we knew about it when we bought it), so we pulled it in and jacked it up to figure it out. I opened the hood to look down on things and noticed the battery wasn't bolted in. It was too big, way too big, so the tie-down bracket wouldn't work. My son put a new battery in the V-6 when the alternator died, thinking the old one was part of the problem, so we had the original. I'd since charged and tested it, so I figured I'd put the right battery in and bolt it down. Silly me! I assumed the battery would fit, but the genius engineers at Hyundai had reversed the post positions, for no intelligent, logical or even conceivable reason whatsoever! (More cussing out stupid engineering ...) By lifting the wiring harness a bit, I found I could get things to line up, but the tie-down bracket still wouldn't fit. The idiots at Hyundai had changed everything, so, ultimately the original, over-sized battery went back in, for now. I also checked the oil and found it very low but figured the front end being jacked up was part of the problem. It ended up taking two quarts. Those tasks accomplished, I went back to my original objective and took a look at the suspension, finding the upper control arm bushings were shot. "Not a big deal", I thought and set the car down.

The big surprise came when I started it. We'd put about 100 miles on it by that time and had no running problems other than the squeaky bushings, but now, it had a hard time starting, wouldn't idle and surged up and down with the RPM's hitting 2500 and then slowing to 500 and dying. Sheesh! What had I done???? It ran great before I pulled it in the garage and an hour later, after adding oil and fiddling with the battery, it was essentially undrivable. I’ve tried the obvious but it won’t run worth a darn (I don’t really cuss, that’s just an expression).

Now I've done a little research on this forum and others and see this is something of an issue with the Sonata and other Hyundais, but there doesn't seem to be a clear-cut reason for, or solution to the problem. And I still have to assume, since it ran great before, something with the oil or the battery had something to do with the sudden change from great to horrendous ... I'm stumped.

While experience has long since convinced me that automotive engineers are, for the most-part, idiots in offices, I've also found the most brilliant of automotive minds to be those who pick up a wrench from time-to-time and know the difference between a 6-point socket and a screwdriver. There’s no substitute for experience. I've also found most of those truly brilliant minds often hang around internet forums, such as this. So, I'm putting it out there for you ... what do you think? Can you help with my conundrum or should I tow the thing to the junk yard (after filling it with several hundred rounds of unused deer hunting ammo)? (I know, not productive but … sooooo satisfying.)

The Scipio Kid

 

You mean what's obvious to you?
That could be different from what's obvious to every one else. After all you are an engineer! ;-)

Did you get any trouble codes?

Tell us what exactly you did and use as few words as possible. Zeros and Ones aren't cheap, you know!

 

Well now, that depends on where you put the comma.

Thanks for the reply, Allegretto. (Is that Finnish?) So, you think I'm long-winded? You've joined an elite group of all the people I've ever known. But, to the point ...
I'm figuring the problem is sensor or computer related rather than mechanical since it happened seemingly as a result of my fiddling with the oil and battery. But I'm not ruling anything out.

The oil level is now 3/16" over max. Is there an oil level sensor I might be messing with?

I tugged on and moved the wiring harness. Is it possible I've pulled a lead off a sensor? This is part of the "obvious" I mentioned. I can't see anything wrong with any of the wiring or connectors after a careful inspection.

When I put the second battery in, there was some question whether or not it was good, so I started the car several times just to work the battery and see if it was weak. Might this have fouled up the computer in some way?

After the V-6 died on my son, we jumped it off my truck and charged it for 20 minutes. When we started it up, it jumped up to 4000 rpm and surged between that and 2000 for about 30 seconds, then settled down. We charged it several times while trouble-shooting and each time we started it, we'd get the same kind of surging. Since we got the new alternator (and battery) in, it's never happened again. Someone posted (on a different thread) the throttle plate position had to be "relearned" by the computer by turning the ignition on for 10 seconds, without starting the engine and then off again for 10 seconds. I tried this and it started normally, idled perfect for 20 seconds until I hit the brake to put it in reverse and the surging started again and it died. Tried the 10 second reset thing a few more times and it surged right off the bat every time.

So it's still screwed up and I'm still clueless.

Oh yeah ... another oddity I've never seen ... it did fire the CEL so I hooked up the code reader. It went through the motions and got to the part where it's "collecting data" and froze, just like Windows 10! Tried it 4-5 times and got the same result so I don't have the error codes yet. Been busy with work so haven't tried Torque Pro yet. I use it on diesels but it ought to work on this as well. Hope to have time tomorrow and I'll report the findings.

Thanks again. looking forward to hearing your ideas.

 

I've been called many things but "Finnish" is a new one. "Allegretto" is actually Italian. More over, I took form the musical jargon where it denotes a certain pace. After all "Sonata" is taken from the musical vocabulary as well.
Indeed when you disconnect the battery in just about any of the OBDII equipped cars the learned data get erased and the computer starts over from scratch. But still 4000 rpm at start - up?
Your tugging on the cables may have affected an electrical connection. Or a vacuum hose got disturbed. You could disconnect inspect and re-connect all the wire harnesses under the hood. Make sure the ground connections are clean as well.
You could trace all the vacuum lines and look for damage or any irregularities.

If you feel like taking a risk you could just drive that thing for 30 minutes or so to give it a good warm up and allow it to re-acquire some data. This would also give it a chance to set a trouble code. I am sure there is a complex relearning procedure that requires a few minutes of driving at various speeds etc. Maybe you can find it on the web.

I know you said it died when you tried to put it into gear. When you step on the brake and you put it into gear the computer will try to raise the idle speed to compensate for the drag coming from the torque converter. Maybe it died because that adjustment did not work.

To me the "obvious things" are these:
Take out the spark plugs for inspection. Check not only their appearance but take note of the make and model number. Make sure you have the correct ones in there.
Check the air cleaner. Is the filter ok? Any damage to the cleaner box? Any cracks in the intake hose? Any oil in the intake manifold? That would indicate an issue with blow-by or faulty PCV valve.

Of course all that is pretty much like shooting in the dark. In any case it will familiarize you with what's under the hood. Having trouble codes would really help.

There is no oil level sensor on this engine. I would not be worried about the oil being slightly above the "max".

 

Thank you, my musically inclined, Italian friend. I assume you play Spanish Guitar?

Good advice. Those obvious items you mentioned, plugs, air filter, etc, I haven't yet checked. When it first acted up, I drove it around until warm, maybe 10 minutes hoping it'd figure itself out and get better. It seemed to while doing 30 for a couple miles but went nutso again when I slowed and killed at the stop sign, then surged all the way home. I also did a quick blow-by test by pulling the oil fill cap (old diesel trick) while running, but all was good, no apparent blow-by. I'll be out of town today but maybe tonight I can do some more testing and get the DTC codes.

Thanks again

 

Scipiokid:
Read again. Did I say I am Italian? No, I said "allegretto" is Italian meaning Italian language. As far as guitars are concerned I am much better at listening than playing.

 

O.K, my, while not really Italian by nationality, but possibly Italian leaning, musically inclined, but not necessarily performance ready (so far as Spanish Guitars are concerned) friend, put on your genius cap.

I told you I’d already test driven the car far enough to warm up and to conclude it wasn’t just a matter of the computer relearning a few names and places (something I, coincidentally find myself doing on a more and more frequent basis of late … the learning thing, not the warming up, I never warm up. I don’t need to, I lived in Norway for a while).

Got a call on the way into town last night there was a family emergency requiring me to drive 40 miles to my Son’s home and back. Decided to take the high mileage Honda but as I was leaving, your suggestion to “take a risk” and drive it longer, explaining the relearning process might be more involved than I’d considered, came to mind and I figured, “what the heck, what’s the worst that could happen?” Fortunately, I lack the mental capacity to dwell on such deep, philosophical questions, so I took the Sonata instead.

It surged and died until it got up to speed. Stopped at 10 miles to pick up my older son who asked, “how’s it running?” I responded, “a whole lot better” and gunned it. It immediately killed and then started the surging and dying thing again, Dang. By the time we arrived at the final destination, after doing 70 on the freeway for 20 minutes, it was running normal. Took a chance and gunned it again and it went right back to a smooth idle. An hour later, it started right up, idled smooth and ran great all the way home. This morning was cold, and the car covered in ice, but it fired right up and ran great! I drove it 5 miles just to make sure and felt so good about it, I let my daughter take it to work.

I’m thinking you were spot on with the “relearning” thing. Sure glad I listened to you. The cruise control wasn’t working last night so I suspect a vacuum leak probably played into the mix and made it harder to diagnose. I’m out of town again for a few days but I’ll report the DTC codes and anything else that happens when I get the time.

Maybe this is the kind of thing that happens to many Hyundai owners and that’s why there aren’t too many final solutions posted.

Thanks Allegretto

P.S. Are you sure that's an Italian musical term? Because I'm thinkin' that's the name of the pasta sauce my wife gets at Wal Mart.

 

Also, we're planning on doing those control arm bushings Saturday. I'll let you know if the job ends up in cussing, or praising the engineers. (I'm already thinking it'll be the former.)

Also again, the V-6 is running great. That sure is a torquey little engine. It runs circles around my wife's Jag.

 

This might be the right time to confess something: There are not many who listen to me and even fewer who are glad about it. For I am known to be a facetious kind of fellow. The few who have listened to me and incurred the inherent risk of such lunacy have now recovered to the point where they are able to consume solid food again. For months on end they were limited to overcooked spaghetti with allegretto sauce. As every half ways experienced shopper of the grocery aisles at Wal-Mart knows this particular recipe is best consumed while sitting on a toilette because the byproduct of digestion may be eliminated in an explosive manner and accompanied with the sound effects of a V6 Sonata engine that is relearning its ways after a serious case of digital diarrhea.

Please make sure that none of your immediate family will get wind of this.

P.S.: I doubt that a vacuum leak is able to cause a cruise control malfunction. I bet that's an electrical issue.

 

Hey Guys,
Sometimes we just can't leave things alone.
One of my sons is an engineer and it never fails when I ask what time it is , I get an explanation of how the watch is deigned and works. Engineers I guess.
Also, I used to be one of those that blamed the engineers for some (less than smart) offerings when it was really the "bean counter" who deserved the credit.
Anyway, as you all know by now it does require a certain period of time at certain speeds etc. to complete a "Drive Cycle" where relearning gets accomplished. Glad you got it all straightened out. As "allegretto" knows , I have a little background with vehicles to the extent my wife will not allow me to touch her Hyundai or the wheelbarrow AND you have to know a GOOD thing when you have it,,,,,,,,,,the wheelbarrow !