coffee77

Have a 03 Impala with 150K miles. Getting a marble like rattle under the car when I hit the gas (not always, but 1/2 the time). Could this be the trans or the water pump? Its hard to locate the noise. It does not sound like its coming from the top of the motor.
Thanks

abaird

My first guess might be that a torque converter bolt fell out.

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2009 Silverado 1500
2002 Camaro Z28(rebuilder)
2005 Yamaha GP1300R

coffee77

Thanks much. I will look into that...

impalalover

my car does the same thing,sounds like you don't have engine trouble if it's like mine it was the type of gas your using,try a different gas station and a highter grade of gas with highter octane in,see what happens

abaird

Thats pretty good advice. I've heard of 3.8s being picky about fuel. In the cases that I've seen though, the check engine light flashes while this "rattle" or spark knock occurs. Are you guys seeing check engine lights?

__________________
2009 Silverado 1500
2002 Camaro Z28(rebuilder)
2005 Yamaha GP1300R

coffee77

I don't get any engine lights when this happens, but I now just realized that it does seem to happen most often when the car has been running for over 30 minutes. When it does happens, I do believe that I sense a definite bog and I want to let off of the gas pedal so that it will stop. The rattle (like pennys being swirled around in a metal coffee can) normally only stops after I let the vehicle cool down. But again, its not a consistant noise. Very weird!

impalalover

use a different gas staion and a top grade fuel