2 Possibilities come to mind immediately:
1) Low coolant and air in the cooling system. As coolant is circulated through the heater core you may hear this noise you describe
2) Perhaps vehicle is "pinging" due to Spark timing advanced too far or the fuel you are using has too low an octane rating for the vehicle. try another grade of fuel. Perhaps a 91 octane if you are using an 89 octane rated fuel.
Maybe that thumping noise is the sound of another car smashing into the rear of your car.
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Is it serious if my car idler is making a noise?
Depends on where the noise is whats making the noise. Can you be more descriptive of where and what?
Yeah, it sure is. What is that?
When you can not figure out why your car makes a strange noise, you take it to a mechanic.
Check your car if there's loosen tool that makes your car noisy when it accelerates.
You have to jump on his car and he will get out to see why the car is making such a noise.
Yes, they tend to do that. They have a lot of moving parts.
Fuel pump
The correct answer is: When the car hit a tree, it made a terrible noise. Since the object is to find the sentence with vague pronouns, it could refer to either the tree or car. It does not specify which antecedent it refers to. * This is a poor example of a vague (unclear) pronoun because there is no noun antecedent. What is making the noise is the collision, not the tree or the car. What is making the noise is "the car hitting the tree" which is not in the sentence.
Sounds like a loose timing chain.