Rough Idle Only In Drive -99 Grand Am

[baddogi]

For about the last 6 month or so, my car idles real rough in drive. In neutral it isn't so bad. I took it to the shop and they replaced 1 motor mount and didn't see anything wrong with the other three. I also had them hook it up to the computer and they said it showed nothing wrong. Basically, the car is fine except that it shakes in drive. Their advice was to replace the other 3 motor mounts. Do you agree? Any advice would greatly be appreciated. Thanks,

[dlwdkh]

Does the car run rough or just shake? Do you see the Tach moving around and does the brake pedal pulse?

[baddogi]

No it doesn't shake In drive (that I notice) and the brake pedal doesn't shake either. Had the brakes re-done last week. When I put it in neutral the shaking gets less noticable. It's only when in drive and at idle when it shakes. The idle speed on the tachometer is "6" which I guess is normal for that car. Do you have any idea what could be causing it? Is it motor mounts like the dealer said? (Even though they aren't broken).

[compusmith]

Is this the 3.1L V-6? How many miles on it?

[baddogi]

No its the 4 cylinder with a/c and all the features. It has 117,000 miles on it.