when idle, in park, foot off the gas, what is the RPM gauge at?

if it's 0.5k or around there, touch the gas a little and see where it gets smooth again, probably 1k. if you want, you could turn a screw under the hood and make it idle at 1k

 

in idle mode the tach reads about 800 rpm. As soon as I step on the gas it smooths out and runs great but taking foot off gas and engine decels the rough vibration starts again. Even tried adding prmium gas to see if that would help-nope!

 

Ok now be really helpful to all and tell us
1)HOW MANY MILES IS ON THIS 2009?
2)WHAT GAS RM87 or RM89 you have been useing? Takes week to two weeks to clean things up a bit even if you add RM94. It is not like magic right away thing. IMHO 87 is crap gas, 89 is what you should be using,91-94 is over kill.
3)IF YOU EVER PUT IN A (intank) INJECTOR cleaner? Regular use is best.
4)THROTTLEBODY SPRAYED DOWN and CLEANED?
5)AIRFILTER?

HINT: based on THAT
DIRTY INJECTORS leaking at idle and messing up mixture
DIRTY THROTTLEBODY not closeing at idle
DIRTY FUEL FILTER due to miles
NEEDS NEW AIRFILTER based on miles.


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I don't know about the engine in the 09 but on the 03 3.5 there are several small vacuum plugs that could get dry, cracked and fall or pop off. Get a piece of rubber tubing and with the cover off use it like a stethyscope. You should be able to pinpoint a vac leak if there is one.

Also fill in your profile with all the info goodies. It helps people not have to guess what your driving.

 

Go to another dealer. They should replace the throttle position sensor (part# 35107-3C100FFF) and perform all available ECU upgrades. There is an ECU upgrade that addresses this concern tsb# ENG 077. Do not attempt to clean or fix the throttle body yourself as this is a fly by wire system (no throttle cable).

 

Hopefully this helps.

 

You bet, will go to a new dealership with this data, thanks Kid appreciate the info.