Vibration under gas pedal when you first start driving


I drove the wife's car yesterday and i noticed that i get some vibration coming from under the gas pedal if i start to drive the car after it has been sitting for more than a couple hours.

Let me explain when it happens...  I get in the car and shift from Park to Drive and i accelerate i feel and hear a vibration coming from underneath the floor under the gas/brake pedal.  This only happens for like two-three seconds and then nothing is felt or heard.  I stopped the car and went into a store and came out and tried to replicate but it wouldn't do it again...  It was only after it was sitting for more than a couple hours that i got back in the car and it did it again....   It is really bizarre has anyone else experienced this?

Thx Joe

What youre experiencing is most likely the following.... (i get it in my 2010 Chevy Traverse).

The vehicle runs a system check of the Stabilitrack system--- this will occur when you start your vehicle- put in drive and begin to move--- you will feel the slight buzz-- and a quick clack- that is felt in the pedal--- when the vehicle reaches about 20 MPH.

So if youre in a parking lot doing less than 20 MPH- it wont run the test... until you lets say pull out on to the street or highway and reach 20.

sometimes you wont feel it because the road conditions muffle out the sound/feel of the test.
But its noticeable when you pull out of your driveway and slowly accelerate and reach 20 mph....

Unless there has been a change since my 2008 MY, the ABS runs a test at about 7 mph, and Stabilitrack at almost 20 mph. Both can be felt as a momentary slight tap in the gas pedal along with a concurrent subtle clacking noise. These are self diagnostic tests are designed to ensure that these safety systems are functional. A failed test would trigger a dashboard warning light.

thanks for the help with this,  pretty sure it is the stability check you mentioned, I drove the car several times this weekend and noticed that the noise happens around 18-20mph.

xrunr78 , I am glad to be of assistance. I believe that there may be a TSB to reflash the car to reduce the intensity and awareness of the safety systems' diagnostic tests. It does not bother me. In fact, I like being "physically" aware that these systems are ready and able.  :thumb:


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