You might have to change the transmission support.
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Autopartswarehouse

 

Replace your motor and trans mounts. Thatll get rid of your vibration.

 

Exactly ! It is 99.% chance it is your motor and/or tranny mounts , the clear give away is that it changes from park / neutral to drive , I have the same issue , but it is pretty subtle and my gen has like 4 motor mounts (1or2 of which are liquid filled and expensive) . But if it is severe (and imagine it would be with 200k + miles) , swap them out .

 

What is the idle speed in P, D and R?

Have you checked the engine mounts. Place the trans in D and R and watch the engine for shaking. The upper dog bone and front mount do wear out.

 

I had a similar problem and the solution turned out to be so simple, I'm almost embarrased. After cleaning the throttle body (and more), replacing the idle control valve (from salvage), testing the throttle position sensor (old and new), and other tests, I was ready to take it to the dealer.

A friend had a mechanic say for me to squeeze the air hose connecting the air filter housing to the throttle body while the car was idling. If the car cut off, check for a hose hole. !$%@@ that's what it was. There was a 3" slit on the bottom that I never saw taking the hose on and off. I always layed it down with the bottom face down. Squeezing the hose cut the car off just like putting it in park - I even heard it suck in air with the first light squeeze just before the car stalled off. I "seriously" wrapped the hose with electrical tape and it now runs like a champ - especially since the throttle body is clean enough to eat off of inside.

Lesson learned - keep checking the simple stuff until you know for sure it's something more complicated. Then check the simple stuff AGAIN !

 

The Aamco transmission place diagnosed "bad motor & trans mounts".

Thank you all for your help.

Just2day,
I will try that "squeeze hose" technique.

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