Slight rhythmic vibration at idle

Tiny
NGB5548
  • MEMBER
  • 2002 PONTIAC GRAND AM
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 150,000 MILES
I have noticed that my car has a slight rhythmic vibration while at idle. I have had it for a while (don't really remember NOT having it), but recently had a ton of work done on my car, including: new spark plug wires, O2 sensors, intake manifold gasket replacement, and a new catalytic converter. I thought this would take care of it, but it hasn't. It seems to be coming from under the center of the car underneath the floor boards, and you can feel it in the steering wheel if you think about it. I did recently get new tires, which I feel is making the engine work harder in general (still breaking them in). I didn't think to bring up this vibration to any of the mechanics, but none of them brought it up, either. And they have been pretty good about letting me know about any observations that they have about the car since they have spent so much time with it. Any ideas as to what this could be? There is also a small click noise that you can hear when the radio is off and the windows are down when shifting from Park to Reverse, to Drive. However, the loudness of the click depends on how much driving the car has or hasn't been doing lately.
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Saturday, March 26th, 2011 AT 9:17 PM

4 Replies

Tiny
NGB5548
  • MEMBER
PS: the air conditioner is not on when this is happening, and is unaffected by turning the air on/off. Also, I feel like there has always been this vibration, but perhaps as I put more miles on my car, the more noticeable it is. I just want some peace of mind to know that it isn't something major like the transmission, etc.
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Saturday, March 26th, 2011 AT 9:38 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
After reading your post, it sounds like you may have a bad motor mount. The motor mounts are set in rubber. If the rubber wears out, you can actually feel the engine vibration through the frame of the vehicle.

You mentioned a concer regarding the transmission. If it only happens at an idle, I really don't feel it is related to a transmission problem. The clicking noise doesn't sound like anything to worry about either. They tend to make a clicking noise when they are shifted. Actually, a broken or worn motor mount could make that noise worse. Have the motor mounts checked. Or you can do it yourself.

Have a helper get in the vehicle. Start the engine, open the hood, make sure the parking brake is on and tell the helper to keep his foot on the brake. Place the transmission in drive. While holding the vehicle stationary with the brakes, push on the gas slightly. If you have a bad or broken mount, the engine will lift. NOTE: If it moves more than an inch in drive or reverse, chances are a mount is bad.

Let me know what you find.

Joe
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Sunday, March 27th, 2011 AT 2:48 AM
Tiny
NGB5548
  • MEMBER
I haven't checked the engine mounts yet, but I did upgrade the fuel I use to 89, and used a bottle of Gumout. And so far it seems to have helped quite a bit. However, the engine seems to be a little louder when accelerating but it is a better trade off.
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Monday, March 28th, 2011 AT 5:36 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
You may have had dirty injectors. That is very possible. If it starts again, check the mounts and let me know what you find. As far as the difference in sound, it could actually be from runnning better.
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Monday, March 28th, 2011 AT 9:14 AM

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