RPM idle needle goes down and bounces back up?

2008 BMW 328XI
246,000 MILES • 2WD
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YANNABEY22
I’ve recently come across this problem with the car at a standstill when the car is not in park the motor shakes and the idle needle goes down and bounces back up. It even shut off on me at a red light. I have a feeling it’s not the battery because the radio and the lights were still on. I eventually had to start the car again. It drives fine but when it idles it shakes. Please help
Mar 5, 2025 at 12:07 PM
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STRAILER
  • ✓ASE Certified Mechanic
  • 54,503 POSTS
  • ASE Certified Mechanic
Sure, this is a classic vacuum leak or a dirty throttle body. Here is a guide to help us fix it and instructions in the images below to help you with your car:

https://www.2carpros.com/articles/stall-at-idle

Use this guide when the engine is cold:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

And this guide to help clean the throttle body:

https://www.2carpros.com/articles/throttle-actuator-service

Check out the images (below). Let us know how it goes.
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Mar 5, 2025 at 5:05 PM
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