Shaking at 60 mph and higher

Tiny
ALEXTTT
  • MEMBER
  • 2005 PONTIAC G6
  • 3.5L
  • V6
  • 2WD
  • 103,000 MILES
Hello, I noticed when i'm on the freeway the car shakes a lot but on the streets it does not shake.

Also when I turn the A/C on the car vibrates a lot also.
Thursday, June 25th, 2020 AT 5:40 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

The vibration from the A/C could be a couple things. A weak motor mount or the engine's idle speed is too low. Do you feel it when you are only at idle and in gear?

As far as the vibration at 60+ have you checked the condition of the tires and have the balance checked?

Here is a link that explains what to look for when checking tires for unusual wear:

https://www.2carpros.com/articles/how-car-tires-work

Let me know. Also, let me know if the A/C issue is only happens at idle and if the RPM's drop lower.

Take care and I'll watch for your reply.

Joe
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Thursday, June 25th, 2020 AT 7:40 PM
Tiny
ALEXTTT
  • MEMBER
  • 59 POSTS
Hello, when the A/C is off and i'm at a stop light the car will idle rough will be at around 400 rpm's then jump up to 900 then stay at about 700 or so. I don't have any codes. I cleaned the mass air flow sensor but still idles weird.
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Friday, June 26th, 2020 AT 12:52 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
On this car, the idle speed is controlled by the power-train control module based on throttle position. There is a APP (accelerator pedal position) sensor, a throttle actuator control module, and so on. What I would suggest is this. First, make sure there are no engine vacuum leaks. Here is a link that explains how to check for them:

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

If there are none found, I would try to service the throttle body. Here is a link that explains that process:

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

Try this first and let me know what you find. Also, the shaking at idle is because the RPM's are dropping so low. One of the two things I suggested should help.

Let me know.
Joe
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Friday, June 26th, 2020 AT 8:15 PM
Tiny
ALEXTTT
  • MEMBER
  • 59 POSTS
After getting 4 new tires and an alignment done, my car no longer shakes.
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Wednesday, July 15th, 2020 AT 5:40 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

That's good news. I'm not sure how the A/C tied into it, but happy to hear it's fixed. Thanks for letting me know. I'm sure your post will help someone else in the future.

Take care and feel free to come back anytime in the future if you need help.

Take care,
Joe
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Wednesday, July 15th, 2020 AT 7:08 PM

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