Rough Idle and get so low it knocks off while driving?

Tiny
TERRENCE EWELL DUGAN
  • MEMBER
  • 1990 CHEVROLET LUMINA
  • 3.1L
  • 6 CYL
  • AUTOMATIC
  • 67,000 MILES
Rough Idle and get so low it knocks off while driving.
Thursday, October 5th, 2023 AT 10:27 AM

1 Reply

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hi Terrence,

Yes, the engine can knock when the idle speed gets too low, I would check for vacuum leaks and service the throttle body and idle air control valve, here are guides to help you fix it:

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

and this guide use when the engine is cold only:

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

https://www.2carpros.com/articles/idle-air-control-valve-service

Check out the images (below). Please let us know how it goes.

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Thursday, October 5th, 2023 AT 12:53 PM

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