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Engine Hesitation

Tiny
RALPH59
  • MEMBER
  • 2007 MAZDA CX-7
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 126,000 MILES
Car runs okay, but when turning A/C rpm's drop and shakes a little bit. Car never shuts off, no check engines lights.
Saturday, December 7th, 2019 AT 12:58 PM

4 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,380 POSTS
Hello,

This is common when you have a vacuum leak or the throttle bore needs to be serviced. here are two guides that will help us fix the problem:

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

and

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

Please run down these guides and report back.
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Sunday, December 8th, 2019 AT 5:24 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This is normally caused a failed engine mount or transmission mount. Basically when they fail and the AC adds the additional load or stain to the engine it causes it to shake. More than likely it will get worse and start shaking or vibrating all the time.

There is a chance that there is a vacuum leak but I would start with the mounts.

Here is a bunch of info on the mounts. Let me know if you have questions.

https://www.2carpros.com/articles/how-a-motor-mount-works

https://www.2carpros.com/articles/replace-motor-mounts

https://www.2carpros.com/articles/vibration-noise
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Sunday, December 8th, 2019 AT 5:35 PM
Tiny
RALPH59
  • MEMBER
  • 2 POSTS
I will check the engine mounts. But, why is it that the rpm's will go down when the AC is turned on? That's when the car shakes a little bit and notice the rpm needle moving up and down. The car never shuts off but feels like it would. If I turn the AC off it works fine.
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Monday, December 9th, 2019 AT 6:16 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,380 POSTS
I would service the throttle bore first. Please let us know. Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response.
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Monday, December 9th, 2019 AT 10:22 AM

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