AM11 engine with ZF6HP26 gearbox (vanquish 2013 with low mileage 16k miles) is revving higher (750rpm) on Park. On Drive it goes calmly 650rpm. The engine gets rough idle when cold on Park.
Any suggestions very welcome.
Thank you and all the best to everyone!

 

Have you had it scanned for codes? 100 RPM difference is very normal from park to drive or reverse. If you are feeling a misfire at idle regardless of gear selection you most likely need ignition coils replaced. After 11 years of service it should have had spark plugs replaced at the 7 year maintenance. If not they should be replaced with the coils. Have it checked for possible codes stored first.

 

Thank you so much for your input. AMDS shows no DTC. All coils, plugs and injectors replaced for OEM new sets just month ago. I suspected throttles need cleaning.
Just an amateur's question. I am trying to understand why RPM is higher on Park vs Drive with foot on brake, in both cases rpm of the gear box shaft should be zero, so converter is loaded the same way?

 

Got it! The intake hose slipped off causing a leak (not visible from the top). Now all goes fine.