Stuck Throttle..

[RS4VR]

(X posted on QW)

I hopped in my RS4 this afternoon after work and hit the S button as I normally do.

Let the car warm up for a couple of minutes (it was 75 outside) and off I went.

I stopped to turn right and noticed something a bit funny about the idle.. I blip the throttle by pushing maybe 25-30% of the range, I lift my foot off the accellerator to start rolling forward, I lift with my foot OFF the accellerator pedal, clutch in and the RPMs fly up, immediately redline and start bouncing off the limiter..

So I immediately figure, the pedal is stuck down.. nope, it's up all the way.

I figured something must be stuck, so I press the gas pedal down a couple of times and on the 3rd or 4th try, the RPMs drop to normal..

At no point in this was the pedal ever stuck.. it always returned to the same normal position, but the throttle does not respond..

I'm freaked out at this point, but i'm 15 miles from home and I figured it must be a fluke..

I proceed to turn right (into an industrial park area), make a left, stop again.

I push the clutch in, try and move forward a couple of feet to get a look at traffic and it happens AGAIN..

Give her gas to move forward a couple of feet, clutch in, foot off the gas, throttle is stuck and goes back up to 8k RPM.

I have to push the pedal down a couple of times and it stops.. blip the gas to move forward, throttle sticks again, for a THIRD time.

I thought maybe it has something to do with the S button, so I turn it off, no effect...

At this point, I shut her down, pissing the people off behind me waiting to turn..

I lean over, no obstructions around the gas pedal, range feels normal, no sticking etc..

I wait a couple of minutes and turn on the car again (leave the S off) and try to get the car to the dealer.. Made it over.. it's after 6pm, service is gone.

Bad news, no one to leave it with.. Good news, the throttle hasn't stuck in the last 20 minutes or so..

I take side streets with no traffic and after about 25 minutes of no throttle issues, I hop on the freeway and luckily, I made it home.

Need to figure out if I should drive the car to the dealer, or have Audi Roadside assistance flatbed it.

I'm not getting the warm and fuzzys about driving this thing again until I figure out what the hell is wrong.

Is there some kind of logging in the ECU that would record the stuck throttle or throw some kind of failure code?

Is there somewhere in the engine compartment I can check to see if there is anything stuck?

Thanks guys!

BTW I didn't see anything on the dash pop up.

[Doug_S2]

I have never seen a dbw car do that. Even if it is ok now I would change the pedal sensor.

If the throttle body was sticking you would get codes and the epc light would come on.

[neckarsulm]

Possibly a fault with the electronic throttle pedal
You need VAG COM to scan for codes and you can also use it to measure what reading the throttle pedal is giving to the ECU, if it shows any signal at all and yet it's fully up then the fault would lie with the throttle pedal.

It can be hard for the ECU to realise that there is a fault in this situation as it can't tell the difference between you asking for 50% throttle and the pedal doing this without your consent hence importance of reading the measured value.

[RS4VR]

It has been behaving a bit strangely (lag etc), but never something like this.

[neckarsulm]

[hadn't read Doug's post when I posted mine]
There was that incident with a BMW many years ago on the A46 that ran out of control and of course Toyotas..

[RS4VR]

After the out of control throttle incident... my ESP disable button no longer works.

Car is at dealer now.. they can't seem to determine the problem.

[Doug_S2]

If they cannot find anything they have to at least change the pedal sensor. Tell the tech to look on the wiring diagrams and check what else shares the supply voltage for the pedal sensor and check those sensors as well.

[RS4VR]

They think the esp disable issue is the switch.. I'll bet anything it is not. The switch is a momentary switch.. when you push the esp button, the esp icon comes up on the dash and then immediately disappears. Hold the button, the ESP icon comes up on the dash and disappears, so it is making contact.

They are not finding any codes and have no idea why my throttle went out of control.

[neckarsulm]

They should be able to use diagnostics to see if the ESP switch is doing anything

[adsgreen]

Most dbw throttle pedals have two position sensors mounted inversely. So as you press the pedal one goes from 0% to 100% whilst the other goes 100% to 0%. the idea is that they should cancel each other out under normal conditions so if one sensor fails the ecu can detect it straight away and usually defaults into limp home mode to prevent this exact problem. I need to check the wiring diagram but would be surprise if it didn't operate like this.

The Toyota is dbw but the stucking pedal was mechanical and would actually have the pedal stuck. There are some stupid people out there who when asked said 'oh yes I have that problem as I have to put my foot behind the pedal and pull it up but thought it was supposed to do that!'

[adsgreen]

Just checked and yes, two sensors.
My bet would possibly be the other end - Perhaps the throttle body sensors and/or actuators are playing up.