Skip the auto shop - Our mechanics make house calls

Q: Car vibrates/shakes when sitting still in idle (in gear or in neutral).

asked by on

After having my car serviced for oil change, tire rotation and air filter replacement, as I was leaving the service center my car had a new engine vibration/shake while in park or neutral in idle. If I rev the motor to 1000 rpm the problem seems to go away. I am not getting any engine codes. I have since replaced all motor and transmission mounts (3 were broken anyway) but this did not make any difference. I have taken the car to Roger Beasley dealership who had it all day and could not discover the issue. It drives fine. Any electrical load while sitting still seems to make the vibration worse. Lights, fan, AC, power windows, windshield wipers, even pressing the brake pedal. This is driving me crazy not to mention making me concerned that something serious is about to happen. Any ideas?

My car has 94000 miles.
My car has an automatic transmission.

This sounds as if you have a low idle condition. I can say your car isn’t likely to suffer a catastrophic failure because of this. With a condition such as this, it is normal for it to run rougher when electrical components are tuned on and it is normal for a car to run rough when the idle is to low.

My first instinct here is to clean the throttle body, fully warm the car, connect a scanner, and command the IAC (Idle Air Control) valve to move the idle high and low to see how it responds. 9 times out of ten, I have found this to fix this symptom.

Other things to consider:

Some more advanced possibilities include the MAF (Mass Air Flow) sensor, which is the primary sensor the PCM (Powertrain Control Module) uses to calculate air-fuel ratio. Although, I wouldn’t go replacing the MAF without a thorough diagnosis from a certified technician.

I’d consider allowing a certified mechanic to diagnose your rough idle if you decide to get this fixed. You’ll have a clear idea of what will need to be fixed after doing so.

Good luck!

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  • Home
  • Questions
  • Car vibrates/shakes when sitting still in idle (in gear or in neutral).

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Stalling,bad fuel mileage,won't start without Acceleration, rough idling.

This may be related to a couple of different things. I would recommend checking the idle air control valve/module which works similar to the MAF sensor in that it regulates air intake as it is mixed with fuel prior to...

Q: Shuts off on first start up but starts right away on second crank. Only happens when car is left alone for a few hours.

Hello, thank you for writing in. You are aiming in the right direction, and looking at the fuel and electrical systems is the right idea. With a starting issue like this, you have a board spectrum of components in which...

Q: Engine smokes on start up

I'm presuming that you bought a used engine and had it installed which can be a risky business. If the engine is using oil and smoking out of the exhaust it probably needs major work. If you bought a remanufactured...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.