2003 Pontiac Grand AM GT shakes when in idle and when going fast?

[Ian A]

I have a 2003 Pontiac Grand AM GT, and recently it started shaking when the engine first starts, when it is in idle, going in reverse, and speeding up (50s-60s).

The check engine light comes off and on, and it turns on when speeding up quickly. Why is this happening? We have taken it to be checked by a computer, but nothing comes up. What could be causing this?

 

[gmtechs]

where did u take it too
if the engine light comes on the code is in there
in history
u may need someone with a gmtech 2 scanner

u sound as if the engine is missing, but u need the codes
before we go further