Is there any way you can get a copy of the data stream engine info?

Before spending a lot of money replacing parts without knowing which was bad is not the way to go.
Certain things do need to be replaced as part of good regular maintenance.
A concern always crops up when we ask where were the replacement parts purchased.
If we only suspect a part is malfunctioning, but can't be sure, we could wind up replacing a good part with a cheap defective part, which stinks !
There are so many cheap junk parts out there and parts replacers can really increase problems without knowing it.
That drop in mileage is something to be checked out and the shotgun method of replacing everything can open a can of worms.

It appears from what was posted , nobody has found the root cause of the vibration and the time has come to bite the bullet and have a competent shop diagnose the problem. Everybody cannot know everything and places that only replace parts cannot be expected to be capable to do an accurate diagnosis.

 

I didn't realize that one could get a copy of the data stream. Interesting. I just have a simple code reader, but I'll ask friends if anyone has a higher end OBD2 unit.

I agree about junk parts. I will put in non-OEM parts in some places, but if I think it's critical I go OEM. The coil packs failed one by one over a year period starting around a year and a half ago. I replaced them with genuine Hyundai coil packs purchased from dealership. I don't remember which brand plugs, but they were a leading brand. I forgot to mention that the forward O2 sensor also threw a code around the same time I had the transmission fluid was changed. I replaced that with a non-Hyundai sensor. That didn't seem like big risk to me.

I had it in the dealership for an inspection about 3 weeks ago. I had them double check the alignment I had done (OK), and told them about the vibration. They took it for a test drive and and felt it was one of the wheels. They found that the left front wheel had a dent from a pot hole, and re-balanced it. That did not eliminate the vibration. I unfortunately didn't tell the about the sudden mpg drop. I was fixated on the vibration and just didn't think of it.

 

This situation has to be costing a lot of $$$.

Any parts relating to engine performance if not up to par, most likely will not correct the problem.
All we can do is remind folks to check where the parts come from and that can tell you a lot.


A little FYI, domestic manufacturers usually try to manufacture decent parts , provide available training for techs, and charge accordingly.
Some places carry lower priced parts that don't always measure up to good quality, unfortunately imported,,, and sometimes Benji gets the bear and sometimes the Bear gets Benji.
If folks are not aware of what the market is doing they are fair game , and they pay.

 

No, the problem itself hasn't cost much money so far. The coil packs were the original coil packs, and they went bad prior to the issue. As I said I replaced them with Hyundai coil packs, so they should be good. I replaced the plugs around the time the coil packs started to go bad, and that needed to be done. The transmission fluid was never changed, and probably should have been before 140K miles. The tires needed to be replaced, and it needed an alignment. The O2 sensor threw an error code, so that needed to be replaced. That did go bad after the vibration started. If the replacement was no good, I would think it would have thrown a code.

Still looking for an ODB2 with data scan. Considering a and https://www.carscanner.info/ on a tablet if I can't borrow something from someone.

 

I have closure on this. The main bearings in the engine went last month. I can't explain why I only felt a subtle vibration in a certain speed range. Maybe at other speeds the light vibration was masked by other things. Don't know. But I knew something was wrong with the car.

The car had 145,300 miles on it, and the bearing recall covers affected models up to 150K miles. Call me lucky. Hyundai installed a rebuilt engine at no cost to me.

Eventually this Sonata will be replaced with another Sonata. I love Hyundai.

 

Believe it or not, a lot depends on your relationship with the dealer service dept.

There are all kinds of people out there, some pleasant to deal with and some otherwise. Having been a service mgr for a different manufacturer, some folks we couldn't do enough for because they were very pleasant to deal with and some others , well no matter how hard we tried, just couldn't please them.

The old saying about getting more flies with molasses than vinegar , is the secret to getting a lot of extras.
Glad you are happy with your Hyundai, Take good care of it and it will usually pay off in the long run.