Quote (Hiroyue @ Nov 29 2023 10:00am)

Ok so coming from a bmw perspective, we have chain driven cam and crank timing. Rough idle can be attributed to a slacked timing system. Could possibly be “leveled” out as you get higher in the rpm because the car has its own knock sensor system and adjust advanced/retard timing to try and compensate for the roughness. Unless codes get pulled to help pinpoint if this cam or crank sensors or vacuum leak causing unmetered air etc, you’re kind of shooting in the dark. If it’s not throwing codes he may be right looking towards internal. If he is saying the tensioner and belt referring to the serpentine belt “for the balancer power steering alternator” yes when they wear out they make noise at idle can cause idle vibrations and make horrible noises at low rpm’s until the belt stops slipping or the bearing spins properly in the idler pulley or tensioner.