there are a number of things this could be, for example. vaccum problem, timing and firing problem, fuel problem, and if the check engine light is on it could be a nubmber of sensors, example, tps, iac, so you just have to start somewhere and go with it from there checking to find out what it really is
want to know if my starter is going bad if
It can, but you should trust the computer diagnostics in a situation like that.
this answer is hard to find
change the water temp sensor
my 2005 ion shakes while idling.. has done this ever since i got it in 2005
A bad throttle position sensor, on your 1991 Saturn, will cause the engine to run rough when it is idling. The engine will run normally at higher speeds.
Cars will use more gas idling than starting the car.
replace the cam sensor
There are a few reasons why a car shakes when idling at a red light. Some reasons could be the ignition coil, motor mounts, or spark plug problems.
The Idle Air Control valve located in the throttle body.
Means you are over heating.
The idle arm may be off set. The idling is set extremely high according to the RPM's stated and need to be lowered.