Skip the auto shop - Our mechanics make house calls

Q: Loud Knock

asked by on

Knocking noise under car after start up, didn't start until put I drive and slightly driven up the hill in my driveway then put in reverse when I notice and came back down. Now at idle loud knocking noise and car barely stays on. After pressing on the gas, the knock dies down but starts back up at idle. Any clues?

My car has 110000 miles.
My car has an automatic transmission.

A: Hi there: In most cases a knocking sound a...

Hi there:

In most cases a knocking sound at idle is caused by metal to metal wear. Some of the common causes of this condition include low oil pressure or low oil levels inside the motor or transmission, damage to suspension or driveline components due to striking a curb, pothole or other object or loose pulley’s that power the serpentine belt or the belt itself that is causing this noise to occur. To know for sure, you should have a professional mechanic complete a car is making a noise inspection; so they can pinpoint the source of this noise and recommend the right repairs.

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

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: my car turned off while going through a flooded parking lot what happened?

Hello, thank you for writing in. This is a difficult situation. When a vehicle floods, the amount of electrical damage that can be done is extensive. Most of the electrical components are weather proof to some extent, but they are...

Q: Car died while idling at drive-thru with no warning and will not restart.

Start with the basics. Have your battery tested so it can be verified as good and at least 75% charged. Ensure that your battery cables are clean and tight. The electrical issues you've had do seem they may be related....

Q: Where is the Crankshaft Position Indicator on a 1998 Infiniti QX4?

The crankshaft position sensor is typically externally mounted on the engine near the crankshaft pulley. I would recommend checking near the crankshaft pulley for this answer. If you need help with the replacement of the crankshaft position sensor, I recommend...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...