Hyundai Repair: 07 Sante Fe Shift Problem, city fuel economy, transmission control module tcm

Question
I have an 07 Sante Fe with Engine braking when coasting between 31-40MPH. RPM’s can reach as high as 1800@39MPH when accelerator is released when between this range. Almost as is I had the car in manual 4 gear.

Once 40MPH is reached, engine will up shift to 5th gear and engine braking disappears when speeds drop back into the 31-40 MPH range.

If speed drops below 30MPH, problem above will reappear when speeds go back up to the 30-39mph range.

Gas mileage is terrible, 16MPG city.

I just picked up the car from the dealer to have them take a look and they said it was normal, and that they were seeing 15-16MPG.

This can't be right! Didn't notice this problem on the test drive.

Thanks for your help!

Answer
I haven't driven enough '07 Santa Fe's to know whether the engine braking is normal.  Since they're claiming it's normal and you say it isn't, your best bet is to probably go back to the dealer and test drive one with the same engine yours has.  

Not knowing which engine you have, it's difficult for me to speculate where you are on the fuel economy curve.  I'll say that customer-reported city fuel economy on the 3.3 Sonata is about 15-18.  Since your Santa Fe is heavier than the Sonata, I'd surmise that 16 is probably on the higher end of city MPGs for the 3.3L.  I'm figuring about 13-16 MPG for the 3.3 would probably be the normal range.  I'd expect the 2.7 to give slightly better fuel economy, maybe about 15-18 city.

Regardless, the engine braking isn't likely the problem with your fuel economy.  The ECM cuts off the fuel to the engine when coasting unless it's necessary to pulse the injectors to keep the engine running.  In fact, the engine braking you feel may be a purposely designed feature to enable the ECM to cut off fuel.

If the new vehicle you drive doesn't display the same characteristics as yours, you're then within reason to ask for an explanation of this.  While I don't know about the Santa Fe's transmission control module (TCM) specifically, one operating strategy of many Hyundai TCMs is to monitor brake usage during coasting.  If you tend to apply the brakes during coasting, the TCM will learn that you do this, and, under some conditions, actually downshift to assist with braking.  Again, though, you won't be using any fuel during engine braking because the ECM will have shut the fuel injectors off.