I have a 2005 Saturn Ion Redline. Whenever I am coming to a stop I put it in neutral when I get to about 15-20mph, and whenever I am rolling into it the cars idle goes up and down by a good amount every second or so. It also happens in reverse. The car idles just fine when I get to a stop. What could the possible issues be?

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Apr 21, 2021 at 9:44
  • Are you braking when it is happening?
    – HandyHowie
    Commented Apr 21, 2021 at 9:53
  • Yes and no, happens when I’m not braking and when I’m braking. Usually below 15mph till I stop. Also never happens while I’m in gear.
    – Frommelt12
    Commented Apr 21, 2021 at 17:07
  • Sounds like something is wrong with the part connected to your gearbox. When you are in gear its movement is restricted so it doesn't go up and down. Maybe try to check the transaxle.
    – whenov
    Commented May 25, 2021 at 2:05
  • "I put it in neutral" - hard to tell here, do you have an automatic or a manual? Some manual transmission vehicles will try to guess at your next gear shift and shift the idle RPMs to match and make your shifts smoother. Commented May 16, 2023 at 12:08

1 Answer 1


This can be caused by a dirty throttle body, even slightly dirty. The throttle body needs to be hospital-room clean. If you do your own repairs, clean out the throttle body with a throttle body spray cleaner and a clean, new, lint-free cloth. Forget about fuel additives -- you need to get in there and wipe it clean, including all sides of all the moving parts and all the surfaces.

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