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Sudden Acceleration Problem with 2009 Hyundai Santa Fe

So this morning on my way to work, my 2009 Hyundai Santa Fe started to accelerate uncontrollably despite my efforts to stop it. I was doing about 45 on Hwy 29, behind a guy slowing to make a left. In a hurry to get to work, I floored it and rounded him as he slowly merged off the highway. I only floored it to accelerate, then quickly removed my foot from the pedal. The car didn’t start to decelerate, instead it continued to gain speed. I tapped the brake as it was acting like it was on cruise, but accelerating to over 60mph… Nothing. I stepped hard on the brake and the car slowly came to a stop despite the accelerator still trying to force the car forward. I put the car in N - it spun loudly into a high pitched rev, I stepped hard on the brake as a back up, still in Neutral, and stomped on the pedal a couple times. It released. Thank God. I cautiously slipped he car into D and went the remaining 300 yards to the parking lot at work. This evening, Hyundai Roadside Assistance came to pick up and yow my car to Vallejo to the dealership. Please help me pray that the find a problem to fix. I got on the internet and found numerous similar complaints and how the dealer can never find the problem so they won’t fix anything. Especially with the baby coming, I can’t have this car “as-is” in our lives. I need a new part whatever that may be or a new car. I just pray this doesn’t cost us more money or headache. ;(

I followed the advice of others here on this blog, and reported the problem to Hyundai and to NHTSA. Now just waiting to hear what they say at the dealership Monday AM :-/

Your throttle stuck open. Nobody can look up problems unless you say which engine you have. Not that it would guarantee an answer, but it gives you a better chance of getting something.

After much research, I think car makers will return to mechanical linkage to the throttle. Sometimes better technology will make things simpler. Maybe we won’t need throttle actuators any more.

Well, there are 4 items involved in the process of opening the throttle in order to increase the speed of the engine:

Throttle pedal assembly
Engine computer
Throttle Body
The wiring between those three parts.

Just about every car made today uses drive by wire systems.
I’m pretty sure your Santa Fe is one of them.

You have a throttle pedal which contains an electrical device that measures how far you are pressing the gas pedal. Supposedly, this device has a back up device built into it, and the functionality of both is checked when the vehicle is started. If it fails this test, the car won’t run correctly.

Next up is the ECU.
The ECU reads the throttle pedal reading, plus lots of other sensor readings, and sends an electrical pulse to the throttle body. Basically, it tells the throttle body to either stay put, open more, or close more.

Finally, there is the throttle body itself, and the electrical motor in the throttle body that opens the plate inside of it, that lets air into the motor. The motor is quite simple. It requires electricity to open. The throttle body has a sensor built into it that also sends a signal back to the ECU to tell the ECU how far open the throttle already is. This sensor is called the Throttle Position Sensor.

Now, the two biggest points of failure are the throttle pedal and the throttle body.

If the throttle pedal sends a bad signal to the ECU, it can tell it that you want more throttle than you actually do, and then the ECU tells the throttle body to open wide.

If the throttle position sensor is bad, and tells the ecu that the throttle is closed when its actually wide open, you can guess what that’s going to cause.

If it were me, I would replace the throttle pedal first, then the whole throttle body assembly second (unless you can replace just the position sensor), and finally the ECU.

You didn’t mention how many miles are on your Santa Fe, but maybe the throttle plate in the throttle body is sticking due to carbon deposits. Maybe pulling off the intake hose, and cleaning it with throttle body cleaner might be worthwhile as a starting point.

Good luck.


There are sensors to determine throttle body position. If the PCM tells the throttle to reduce or close and it doesn’t, that causes a major error and the PCM will go into a failsafe mode. The engine will deactivate cylinders to bring the engine back down to idle speed.
Since this didn’t happen, it’s pretty safe to assume that throttle body sticking or other problems aren’t the issue.

Most likely, the gas pedal was stuck down. If it wasn’t a floor mat issue, then the pedal assembly should be suspect.

I remember reading somewhere that this issue with this particular car is often caused by a defective throttle position sensor. This may be something to look into with either an Internet search or asking at the dealership. It still doesn’t really make sense to me that the TPS can cause a problem like this, but apparently it can on this car. Something for you to look into…