ok well i have a 2000 trans am ws6 and for some reason sitting still the idle is fine but as soon as im going down a hill or really anything and i put the car in neutral(6 speed) the idle does not sit back down to its original it has done it from the time i got it and nothing i have found will fix it so if anyone has any suggestions it would be great thanks

 

Do u put the car in nuetral as u are rolling along and the idle is up. Then u come to a stop then the idle comes down as the wheel speed sensors see zero mph? Mine does just that. I think it is in the program somehow.

 

Mine done this as well. I found that the vacum hose going into the intake behind the TB on passenger side had a hole in it. I know it doesn't sound right but as soon as I replaced the hose it stopped.

 

Its a vac leak or tb is not compltely closing. More than likely a leak in pcv lines going into tb and or intake.

 

This is exactly what mine was. The hose after the PCV valve right before the throttle body was cracked. It's a super common thing with these cars. I chased this demon for 2 years before I found it by accident.

 

Always a vac issue lol