Hyundai Repair: 01 accent vibrates when ideling in drive, intake manifold gasket, vibration frequency

Question
my wifes 01 accent runs smooth till its put in drive, then it has a heavy vibration until you give it some throttle then it smooths out till its back to idle, then it vibrates again,it does not vibrate in reverse, could this be a bad front or rear roll stopper?  thanks in advance

Answer
Is your check engine lamp on?  If so, it's unlikely to be a mount issue.  If not, then the roll stopper is a plausible explanation.

Vibration frequency can often be a great assistance in diagnosing the cause.  Are you familiar with the frequency of a single cylinder misfire?  If it's at that frequency, then you're likely looking at an intake manifold gasket leak.

If the frequency is about double that of a misfire, you could be looking at a low idle issue.

If the frequency is about four times that of a misfire, you may well be looking at a motor mouont issue.

Since this only occurs in drive and not reverse, it's also possible there's a wire broken in one of the harnesses that stretches apart when idling in drive, but touches all other times.  I've seen stranger things.