Originally Posted by Nebraska1990LE
I can't figure out what'* causing my car to shake...it'* not really a shake though.
It'* kind of a hard thump going back and forth from front to back. There is no side to side movement or vibrating...just front and back.
It almost feels like somebody pumping the brakes. it doesn't do it all the time but will go for 10-30 seconds every once and a while.
Sounds like you might have one spark plug that'* not firing all the time. Have you performed any maintenance on this car recently? If not, I would do your basic "tune-up". Replace the Spark Plugs(Not Bosch, stick with OE Delco), Wires, Air and Gas Filters, PCV, and O2 Sensor(again, NOT Bosch).