Skip the auto shop - Our mechanics make house calls

Q: The car I'm interested in buying has an engine knock

asked by on

I want to buy a 2003 toyota celica but the engine has a knocking sound what could be wrong?
My car has an automatic transmission.

Engine knock by definition means the combustion taking place is mistimed or improperly detonated. More technically it means the explosion(s) has taken place partially or completely outside of the "envelope" (or area in the cylinder that is designed to push the piston down correctly). This will create an audible knock that can be heard during idle and while driving. One of the reasons it happens is due to the wrong octane rating, however in your vehicle that should not be an issue.

The spark plugs/wires and carbon deposits can also cause engine knock. You may want to inspect and possibly replace the distributor, spark plugs, or wires. Inspect the plugs for excess carbon build-up, this will tell you if the carbon deposits are a factor.

There are other parts that can cause a knocking sound that is not by definition "engine knock". If your engine’s rod bearings are wearing down, they can cause a knocking and be a sign of a much larger issue. You will want to look further into the knocking and see if you can pinpoint where it is coming from.

I would highly suggest having a pre-purchase inspection be done on the car by a certified technician, like one from YourMechanic. By doing so they will be able to diagnose this issue and pinpoint any other issues that are present prior to buying the vehicle.

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!

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: Car stalls after reaching operating temp

Depends on if the engine is overheating or not. It would not stall on turns only, if it was overheating. It would stall a lot more often than that. You may have a problem with the EGR valve sticking open...

Q: Where to buy a radio with a casette player for a '96 Celica

Go to junkyards. There are tons of them on junkyards. One of the first things I do when I get racked cars is take the radio system out, put it inside in the garage so it doesn't get ruined in...

Q: Hi Patrick, I was told by my machanic when my engine light sparked in that I need a oxegen sensor, and said that it has to be fixe

Oxygen sensors are tested using an automotive scope or oscilloscope. In your circumstance, if there are more than 100,000 miles on the sensor, the sensor output should be verified on a scope. The mechanic should show you the output waveform...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.