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Car Sounds Loud When Idling But Drives Fine – Is This Ok?

Your car seems to be running fine but when you accelerate from idle, the car sounds like it's going to blow a gasket. If you are experiencing this problem, then this article is for you. We've put together some information from expert mechanics about the symptoms and potential causes of this issue.

If you hear your car idling louder than it should, it can mean that you have compression loss in one or two cylinders of your car's engine. Compression loss is likely to happen as a result of the daily wear and tear of car use.

Compression loss is one of the most common problems that occur in a car. Continue reading to learn more about what causes compression loss and the telltale signs that your car's engine has it.

Portrait of a mechanic at work in his garage, Car Sounds Loud When Idling But Drives Fine - Is This Ok?

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What Causes Compression Loss in a Car Engine?

Close up detail of new car engine

Compression loss is the last thing you want to happen in your car engine. This is because it causes problems with the engine's performance. It is also one of the first signs that you should pay attention to when you notice any issues with your vehicle. 

Compression loss is a condition where the compression in the cylinders has decreased. This causes less power and poorer gas mileage. This is caused by low oil levels, oil leaks, or improper valve adjustment.

The most common causes of compression loss are:

Worn Out Camshaft

As you probably know, the camshaft is driven by the crankshaft. When a camshaft becomes worn, it begins to slip on the crankshaft.

This causes more power loss than just a worn valve. It also causes higher RPM's as the camshaft does not turn at the same rate as the crankshaft. 

Loosened Timing Chain Tensioner

One of the most common causes of compression loss is a cracked timing chain tensioner. This happens when the chain is stretched too much and breaks.

A broken timing chain tensioner will not hold the chain tight, causing excessive movement between the crankshaft and camshaft. This will result in lost power and driveability problems. 

Loosened Timing Belt Tensioner

A weakened timing belt tensioner is the most common cause of timing belt failure. The tensioner moves the timing belt and, therefore, the engine crankshaft.

If the belt wears too much or loses tension, the timing belt will not move the crankshaft properly, and the engine may not start or run correctly. This problem is prevalent in vehicles with automatic transmissions, especially those with heavy use.

broken cylinder block close up

Damaged Cylinder Heads

You will lose compression if you have damaged or worn out the cylinder heads. This will show up as a loss of power and even possibly a loss in performance.

The damage may be to the valve guides, the valves themselves, or piston rings around the cylinder walls. These parts can be repaired or replaced with a new set. 

Blown Head Gaskets

A blown head gasket is an important cause of engine failure. The head gasket is one of the most critical components of the internal combustion engine, and if it fails, the engine will either lose power or stall.

Additionally, when a head gasket fails, it will leak oil and cause the engine to overheat. 

Leaking Valves

The most common cause of compression loss in engines is the failure of a valve to close fully. This can be due to a valve that is stuck in an open position or a valve spring that has stretched to the point where it cannot hold the valve closed against its own spring force.

If a valve is stuck in an open position, you will often notice a loud popping sound as the gas pressure pushes the valve back into its seat.

Worn Piston Rings

In a piston engine, as the combustion chamber fills with fuel, it is compressed. This compression can result in excessive heat, leading to the thermal breakdown of the cylinder walls' material.

In some cases, the piston rings, which seal against the cylinder walls, can wear out. When this happens, the rings begin to leak gas into the combustion chamber, thereby lowering the pressure and volume of the combustion chamber. 

The decrease in pressure and volume results in lower engine efficiency since less energy is transferred to the crankshaft.

Watch the video below to learn more about the causes of compression loss and how to diagnose the issue:

How To Diagnose Compression Loss in Car Engine

Compression loss can cause all kinds of problems in your car engine. One of the most common problems with compression loss is a lack of power.

If you don't have enough power, you will not be able to drive your car at high speed. You also might not be able to go uphill if you have a problem with your engine's compression.

If you suspect that your car is suffering from compression loss, it can be a very frustrating issue to deal with. The good news is that you can get the best compression loss repair in your area by contacting an expert mechanic, but the bad news is that it might be time-consuming.

In this section, we'll explain how to diagnose compression loss and what you need to do to fix it.

Compression Loss Symptoms

The main symptom of compression loss is a decrease in engine power. However, there are some other symptoms as well. They include:

  • Excessive smoke from the exhaust
  • Decreased engine performance
  • Engine misfires
  • Trouble starting the car

Other symptoms include

  • Increased oil consumption
  • Increased oil filter wear/changes

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Excessive smoke from the exhaust

Excessive smoke from car exhaust is one of the most significant signs that something is wrong with your vehicle. However, the exact cause of excessive smoke can be hard to pinpoint when it comes to internal combustion engines.

The problem may be caused by a fuel injection or ignition system malfunction. In any case, excessive smoke can usually be traced back to one of these two components.

There are many reasons why the air/fuel mixture is not getting to the engine cylinders at the correct times, which could lead to excessive smoke.

Decreased engine performance

Decreased engine performance is a common problem with most cars. Most car problems are caused by a lack of maintenance or poor repair work. The cause of the problem may be as simple as an oil change or as complex as a blown head gasket.

Engine misfiring

Engine misfiring is a common problem. It can be a big problem if not fixed properly, leading to further engine damage and even burning out the engine.

The reason is that the spark plug wires may be damaged or a faulty ignition system. Another reason for this problem is that the engine may be starved for fuel due to a clogged fuel filter. 

Angry businessman

Trouble starting the car

If you're struggling to get the car started, your vehicle may suffer from compression loss. This means the engine isn't getting the fuel it needs to produce enough power and cause the vehicle to start.

There are several causes for this, including a bad fuel pump or a problem with the fuel injectors. If you notice these symptoms, you can contact your local mechanic, and they will be able to help you diagnose the issue and find a solution. 

Increased oil consumption

Increased oil consumption happens when there is compression loss because of worn-out pistons. The pistons are the main components that compress the air-to-fuel mixture.

If the pistons are damaged, oil tends to leak into the cylinder, and it takes more oil to lubricate the piston. You may notice that your oil levels are too low too soon and that you must top up your engine with extra oil. 

Increased oil filter wear/changes

You may have to change the oil filter too soon if your car engine is experiencing compression loss. This is because the oil filter is filled with metal shavings from a bad timing chain, which can get trapped in the filter and clog it up. 

What is Considered an Average Idle Speed for a Car?

 Detail of Mini Cooper Clubman S small station wagon. Rear end of the car parked on the street. Featuring "bar doors", JCW exhaust and low profile tires..

The idle speed of an engine can vary significantly. The actual idle speed will be affected by numerous factors, including IAC (idle air control motor), air filter quality, and engine condition.

These factors all contribute to a variation of the actual idle speed, which in turn causes variations in the engine's power output. 

Typically, an idle speed of 600 to 1,000 RPM is considered average. Anything less or more needs to be adjusted accordingly. Check your car's manual or consult a mechanic to determine the appropriate idle speed for your unit.

In Closing

car maintenance and repair - mechanic writing checklist paper on clipboard

Your engine is a complex machine, and one component can have a domino effect on another, leading to unexpected or unwanted behavior. Knowing the cause of why something isn't working as expected will help you to diagnose and fix the problem. 

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