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Lumpy Idle 98 S320

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Old Aug 21, 2019 | 09:58 PM
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W140 S320
Lumpy Idle 98 S320

Hello,

My S320 is having this annoying lumpy idle I cannot for the life of me figure out. I've already changed the plugs, wires and coils with OE parts. I replaced the air filter, MAF, brittle clear vac lines that run near the front of the valve cover, cleaned the throttle body and used techron fuel system cleaner. Heres the video where you can see it happen.

You can hear that I shift from P to D. When I shift to D, the idle drops (I assume normal) but also as the same lumpy feeling. Its a rhythmic RPM change and you can see it on the tach so I ruled out bad mounts. Please can anyone point me to the right direction? No faults stored or pending. It's a 98 so it doesn't have the bad harness issue. It's driving me nuts. Thanks.
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