I’ve tried searching for similar threads and have had no luck. My 04 has been throwing the P0505 code(Error in the IAC system). When I start it I have to give it a little action with the gas to keep it alive, which I expected. I didn’t expect it to impact how my car runs at higher speeds however. When I’m at 45 and 60MPH the vehicle vibrates pretty hectically only when I keep a constant speed with the throttle. When I let off it stops. Any chance this is a common thing or am I experiencing yet another issue? Thanks in advanced for any insight!