Something really strange happened to me today. I was stopped at a red light with the car in drive and my foot moderately on the brake when the RPM's went to 5,000 and the car wanted to take off, my only recourse was to turn the ignition off. When I restarted the car everything was OK. Later on I tried this: car in drive, left foot on brake, right foot on accelerator and I could not get the RPM to go above about 2,500, unless I applied extreme force on the brake which I did not as I thought something would give out.

Has anyone ever experienced anything like this? This car is not safe to drive right now.

It is very easy to depress the brake and gas pedal the same time if your foot is placed towards the right side of the brake pedal. It has happened to me twice. I have since trained my foot to hit the pedal near nthe center. Part of the problem was rt knee replacement so leg and foot was lazy.

What confuses me is the 5K RPMs. On automatic tranny cars there is a test called the "stall test" where by you put the car in drive and step on the gas. Usually the RPMs won't go past 2.5-3K RPMS... due to the load the torque converter (multiplier) loads the engine down.

If your car did go to 5K there has to be two problems. 1. What made the engine race to begin with and 2. How did it get to 5K... was the car in neutral?

Something don't compute.

Yeah that's right - if the brake was on, the engine would have stalled before it hit that high RPM. It could have been some kind of gremlin in the fly-by-wire throttle components, I don't know very much yet about how those are laid out, or which components tend to fail.

Sounds like a call to the dealership is in order!

A fly by wire has no mechanical cable from the pedal to the throttle body. Instead the gas pedal is connected to a rheostat (volume control if you will). The rheostat is connected to the Electronic Control Module (ECM) which connects to an electric motor that opens the throttle body.

Essentially when you step on the gas you’re just “asking” the ECM to open the throttle body and increase engine RPMs. It makes the decision.

There’s been a lot “myths” about unintended acceleration… remember the Audi 5000… people claiming they stepped on the brakes as hard as they could and the car still accelerated. Anybody who ever dragged raced their automatic tranny knows brakes are stronger than engines. We stepped on the brake and floored the accelerator… the engine went up to about 2.5K, release the brake and go. The engine won't stall becuase of the fluid coupling in the torque "converter".

In order for any car engine to go to 5K RPMs it needs to be in gear, accelerating in motion and the brake off or the tranny is in neutral… connect the dots.

This post has been edited by raw6464: Jun 2 2008, 08:08 AM

Right, the rheostat in the pedal is like the throttle position sensor, the more it opens, the higher voltage passes through. That's why I'm not sure if it's that, or some other part on the throttle body, that would have caused it. A neighbor's Jeep was racing to 3000-3500RPMs at idle (in neutral) last weekend and I said, "TPS"... pulled the DTCs and sure enough, it was a bad throttle position sensor.

The car was definitely not in neutral. I started it about 30 seconds earlier and had my foot softly on the brake at first. As the RPM's increased I had to press the brake harder and harder until I finally turned the car off. I was watching the RPM's increase from 500 to about 5000 over about 1-2 seconds. My wife thought that my foot may have slipped off of the brake pedal, but the car only moved inches as the RPM's increased. Had my foot been on the gas at 5,000 RPM I would have been well on my way.

Thanks for your response. Today I made an appointment with the dealer, will let you know what they say.

With all due respect my friend, I don't doubt for a minute your cars engine increased unintended. But if you tell the service writer the RPMs went to 5K... you might compromise your credibility.

Before you go to the dealer start your car, put it in gear, step on the brake as hard as you can and floor the gas pedal... for no more than 5 seconds.

The RPMs should top out a little over 2500 RPMs which is typical of most cars... this is called a stalled test. I know this because I did it on my Azera. And it is a very common test done everyday by service people.

If your car does go to 5K you have more than an unintended problem... your tranny is broken also... and you should know this going into the dealer.

From the Hyundai Service web site:

...perform the "STALL TEST"
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Specification : 2100~2800 engine rpm
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Take this for what it's worth.

This post has been edited by raw6464: Jun 2 2008, 06:46 PM

I don't doubt the stall test for one second. I even tried at home with one foot on the pedal and the other on the accelerator and stopped at 2500 RPM as I thought that something would break. On the other hand I do know that I saw the RPM's increase, 3,000, 4,000, and up to around 5,000. Maybe one of the computers went !@#$% for a moment. I agree this is strange, but I did not image. Maybe in a few more years, but not yet. Tomorrow it goes to the dealership and I will report back.

Well, the dealer said that there were no codes and that they could not find anything wrong. For now I will wait and see. If it happens again, I will certainly be taking different action. Maybe it was a one off and will not re-occur.

I have recently had the same problem with my 2004 xg350...once in forward stopped at a light...another when starting the engine and putting it in reverse. Both times with foot on brake.

I can't remember exactly if it requires the check engine light to come on and a code to be thrown, but I know that there is a TSB out about the APS (acceleration pedal sensor - that "rheostat" that you are referring to) having to be replaced. I think it has to throw an APS code before they will replace it though. I think the few we've had come in had only a check engine light and no symptoms. Might check into it though.