Developed a rough but temporary idle?

Tiny
SURFERGURUDUDE
  • MEMBER
  • 2009 MAZDA MX5
  • 2.0L
  • 4 CYL
  • 2WD
  • MANUAL
  • 78,500 MILES
After replacing a 9-year-old battery my Mazda developed a rough but temporary idle. At every stop it will idle rough for about 5 seconds and then it's fine. It must be stopped to heal itself. If I'm coasting in neutral, it doesn't stop the rough idle until I'm stopped. Cleaning the MAS and throttle body didn't help.
Saturday, July 19th, 2025 AT 12:51 PM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
This is typical of the vacuum leak, it takes a few seconds for the computer to adjust the mixture from its normal position to make the engine run smoothly again, this problem might get worse as the leak gets larger. Here is a guide and video to help with the problem, please go over both.

https://www.2carpros.com/articles/repairing-engine-rough-idle-issues

and

https://www.youtube.com/watch?v=LRKWV4Are5c&t

Please go over these guides and get back to us.
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Sunday, July 20th, 2025 AT 10:16 AM
Tiny
SURFERGURUDUDE
  • MEMBER
  • 2 POSTS
I removed and cleaned the throttle body and O ring with MAS cleaner and my idle is back to normal. It may have been the cleaning or maybe just making sure the hose clamps were tight, not sure, but it's all good.
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Monday, July 21st, 2025 AT 12:10 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Thanks for letting us know, we are here to help, please use 2CarPros anytime.
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Monday, July 21st, 2025 AT 5:44 PM

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