Idle high and dips low?

2012 CHEVROLET MALIBU
188,000 MILES • 2.3L • 4 CYL • 2WD • AUTOMATIC
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PAGE0210
The rpm dip low constantly and the car acts as if it wants to stall. Rough uphill and definitely difficult to get it to highway speeds.
What I've done
- changed out both catalytic converters and the downstream 02 sensor. The upstream 02 sensor they ordered was wrong so it's disconnected but the problem was before this.
- Checked for air leaks at the intake and manifold. Manifold has a small crack but I don't think that would cause this?
Any ideas would help out significantly. Thank you guys for your time you are awesome!
Feb 27, 2026 at 1:05 PM
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STRAILER
  • ✓ASE Certified Mechanic
  • 54,494 POSTS
  • ASE Certified Mechanic
Your are welcome, we try to help the best we can, the line "Manifold has a small crack" can be the problem, this condition is indicative of the vacuum leak, can you upload an image of the crack you see? Also, I would remove the throttle body and service it. Here are two guides to go over to help fix the problem.

https://www.2carpros.com/articles/engine-idles-too-high

and

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

Please go over these guides and get back to us. Ken
Feb 28, 2026 at 10:05 AM
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