I thought I posted this earlier, but can't find it. So maybe I didn't hit the post link.
Any my 1998 Acura CL 3.0 has not been started up for about 6 weeks until today. I started it and it would shake the entire car it was running so bad. Like a very low idle. It also sometime will serge, up an down. I took it by Advanced auto and they put the machine on it and said it needed a very expensive idle sensor. Does this sound correct? If so how did this thing go bad sitting in the yard. Thanks for a rapid response.

 

if the idle is bouncing up and down and acting up than it could be that you need to clean the iac valve.. there's a few threads about this problem just search you'll come across some info

 

You might also want to take a look at your engine mounts. I have a bad vibration at idle and a support arm on my front mount is completely cracked. Here is an explanation:

https://acurazine.com/forums/1g-cl-problems-fixes-71/how-fix-2-2-2-3-vibration-idle-689195/