My 2002 Grand Am GT 3.4L V6 has been shuddering/shaking when I come to a stop in idle, i.e. at a red light, or stop sign, etc. I cannot diagnose the problem. I was curious as to if anyone has experienced the same thing and solved the problem.

Most likely it's the idle air control valve. This valve does nothing more than to create a vacuum leak at idle and cold startups to act as a choke. For various reasons this valve will carbon up from time to time creating a vacuum leak at low rpm idle causing the problem you described. To fix the problem, disconnect the electrical plug, take out the two screws that bolt it in place and remove the valve. Then clean both the valve and the port that the plunger seals against with a solvent. Then reassemble.

Thank you for the tip! I will give it a go and see if that fixes the problem then let you know if it helped. I appreciate the help a lot, so thanks again!

Do you have a solvent that you would recommend for cleaning this type of valve?

I usually use lacquer thinner. You could also use acetone/fingernail polish remover.

Turns out it was actually a vacuum leak. Thank you for the help though I appreciate it!