Car runs but knocks
My car starts but has a knocking noise. And every once in a while it idles out.
Experienced mechanics share their insights in answering this question :
Hello. It sounds like there may be something inside the engine that is worn out or broken. This will cause a knocking noise and could also cause the truck to shut off. A compression test checks the compression of each cylinder, and can help to identify the problem in your engine. I would recommend having a certified mechanic inspect your vehicle’s knocking noise in order to have this issue resolved.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
One of the most common causes of engine knocking is low oil. If your car has been using more oil than usual, it`s a good idea to top it off. You can also try using a higher-quality oil, as this can help reduce engine wear. It`s important to regularly change your oil because dirty oil can also cause knocking.
The most common reasons a Chevrolet Trailblazer engine makes a ticking noise are low oil level or pressure, an issue with the ignition system, or an exhaust leak.
Low Transmission Fluid: For both manual and automatic transmissions, the primary cause for whining when in gear is low transmission fluid. If the fluid is too low, then the internal components of the transmission are not lubricated properly.
If someone complains about a “diesel” sound, my first suspect would be some kind of exhaust problem. The exhaust sound is not being properly muffled. This sound can vary, from like firecrackers going off, to a put-put-put sound. It depends on where it is sourced, and how open the sound is to the environment.
When your engine is running smoothly, the air/fuel mixture burns up in a single, controlled detonation inside each cylinder. Detonation knock is a knocking noise that you`ll hear when the air fuel mixture in the cylinders is detonating in more than once place at a time.
Over time, as engine oil starts to gather dirt and increase in viscosity, the interaction between the camshaft and tappets begins to wear down both components to a point where an audible noise can be heard between them as the camshaft spins and the lobes lift and then drop the tappets.
Lifter Ticking
If a lifter goes flat, or won`t hold pressure, you`ll likely hear it begin to make noise. Often, a lifter tick will be most prevalent as soon as you start the engine, and may get quieter or disappear completely as the engine warms up. You may also notice the sound is more prevalent at idle.
Whirring or Whining
Whirring and whining noises from the engine vary as the car runs fast or slow. These sounds can indicate a number of different problems, including a failing water pump, a bad power steering pump, low power steering fluid, a failing alternator, or problems with the air-conditioning system.
While the transmission is the most likely cause, whining while accelerating can also be caused by low power steering fluid or more serious damage like faulty alternator bearings, a malfunctioning water pump, a broken piston or a bad AC compressor.
Worn Ball Joints: Ball joints allow control arms and steering knuckles to adjust to movement. They must be well lubricated in order to do their job, but the grease can wear out over time. When this occurs, expect to experience noise and deterioration.
Mostly its because the faulty fuel pump, faulty ignition starter, wrong camshaft timing, even some dirt might accumulate in the spark plugs, also a cold start might make your car sound like that of a diesel.
In a diesel, the fuel is ignited by high pressure and temperature inside the cylinder, rather than by a spark plug. The clatter is the result of fuel not burning as evenly as in a gasoline engine, creating a knock. Unlike knock in a gasoline engine, the knock in the diesel is not generally a threat to the engine.
If you`re hearing noises like engine knocking or tapping, it can indicate that the vehicle is running low on oil. It may also mean that an engine part, such as a valve or lifter, is wearing out. A whistling noise can indicate an engine belt is misaligned or there is an intake leak.
Once an engine starts to knock, the rod can fracture without warning. It could be the next time you start it in your driveway, or it could keep going for six months. Eventually though, the engine will blow and you`ll be stranded somewhere.
An engine knock can usually be attributed to a detonation problem, which is why the knocks shouldn`t be ignored. Bad engine detonation can cause catastrophic engine failure if the problem is left unchecked. Techway Automotive can inspect your engine and find the cause of your engine knock.
Loose tappets usually make a clattering noise..so loud that it can be noticed easily during cold starts and the sound comes down as the engine warms up.
There is a rattling sound. A lax timing chain, or worse, a broken timing chain with loose parts within the engine, will produce a rattling sound when your car is idling. This rattling sound is typically most prominent while the engine heats up and disappears after some time.
Dirty fuel injectors can lead to a ticking noise in the engine because they can lead to misfires producing a ticking noise. Misfires occur when the air-fuel mixture in the combustion chamber fails to ignite or ignites at the wrong time. This situation causes a momentary loss of power and a ticking noise.
When the timing belt starts to wear out, it may create a ticking sound inside the motor. This warning sign may also be an indication of low oil pressure or the engine not having the proper amount of lubrication.
A phenomenon can occur called lifter tick, where the lifter itself makes an irritating ticking or tapping noise. Depending on the severity of the problem, you may hear an occasional tick or the lifters will constantly tick the whole time you run your car.
The most obvious symptom of a faulty hydraulic lifter is the noise it creates in your car`s engine. You can usually distinguish the faulty lifter by the distinct sound. Instead of a knock or ping, a faulty hydraulic lifter will usually make a sound more reminiscent of a tapping sound.
What sound does a bad water pump make? Any high-pitched sound, or an increasingly loud whining sound as you accelerate is usually coming from the car water pump. The same sound happens when a belt is loose, or the bearings are bad. No matter which of these it is, getting your car to the mechanic is a must.
Loud squeaking or squealing noise while accelerating could mean there`s a problem with your engine belt. It could mean the belt`s loose or worn. Or it could mean that one of the belt`s pulleys is starting to fail. Loud rumbling noise when accelerating might suggest there`s a problem with your exhaust system.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Replaced alternator on car 2 times each time shows it’s charging 14v let car run for a little bit then test drive and car voltage
ANSWER : There are reports that the replacement alternators will not communicate with the engine computer and will not charge correctly. I recommend using only the manufacturer approved replacement part. It can be new or remanufactured but approved for use in the vehicle. Some lower cost alternators on the aftermarket will have charging problems since they will not communicate with the ECM on the vehicle and will stop charging.
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Power steering loss, no belts are turning but the car is running fine. I also have a soft pedal. Whats wrong with my car?
ANSWER : I have only seen this situation once in my 30+ years and it turned out to be a broken crankshaft pulley. Belts are driven by the engine. The crankshaft pulley spins the belts, which in turn spin the air conditioner compressor, power steering and water pumps, and the alternator. The vehicle should be towed to your local repair shop and not driven. Without the water pump spinning to circulate the coolant, the engine will quickly overheat and result in more extensive damage.
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Fuel EVAP line that runs under car is kinked how do I know if it is leaking? Also can I drive it like that if it’s not leaking?
ANSWER : Hi Ricardo. We answered your question earlier. However, if you didn’t receive the reply, here is what we stated earlier. In most cases, an EVAP leak will create an OBD-II trouble code. The best way to detect an EVAP leak is by having a professional mobile mechanic complete a check engine light inspection, they will be able to download the code and determine the source of the leak. That’s the best advice we can offer you. Thanks.
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After you sit with the car running, the car starts smoking and eventually starts shaking
ANSWER : Hi, thanks for writing in. It all depends where the smoke is coming from. If it is from the exhaust then your engine be running rich and starting to foul out the spark plugs. Have the computer tested to see if any codes are present that could indicate what is causing the smoke. If you see smoke from the engine compartment then you may be running the engine hot due to low airflow over the radiator. Have the cooling fan checked to make sure it is running. If it is running and the vehicle has the AC running and the blower is on or near high then you may be using more energy than the alternator can keep up with. This can cause the radiator fan to not turn as fast as it should and let the temperature to rise if idled for long periods. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.
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I put the wrong key in my car and a few weeks later my car just shut down and it will not start I believe it’s the computer but…
ANSWER : Hi there. What had happened is the wrong key set the security to the vehicle. This is to prevent the vehicle from starting with the wrong keys. Try removing the battery cables (+) and (-) for 13 minutes. During that time, put the original key in the ignition and turn it on. Activate everything in the car even though there is no power. Then remove the key and hook up the battery cables. The computer should have reset and reset the security. If the security is still being tripped, then I recommend seeking out a professional, such as one from Your Mechanic, to help you
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I have a mini r53 s (supercharged) runs fine but when car stop and AC is on for a wile car overheat
ANSWER : Your question makes me think of a case I ran into a few years ago. The owner had modified his car but when he installed his fans, one of them was wired backwards so the fan ran in reverse. The two fans were fighting each other which was just like having no fan at all, so the car heated up while it was sitting still then it cooled off when moving. Check the rotation of both the fans before you check anything else. If that’s OK, you may be able to track down the problem with a non-contact thermometer, follow the course of the coolant with the beam. The radiator should be about 30 degrees or more cooler at the exit than at the entrance. If you need help with this, contact Your Mechanic. They can send a technician to your home to check out your overheating problem and let you know what can be done for it.
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Fuel EVAP line that runs under car is kinked how do I know if it is leaking? Also can I drive it like that if it’s not leaking?
ANSWER : Hi there. In most cases, an EVAP leak will create an OBD-II trouble code, which is the best way to detect an EVAP leak. By having a professional mobile mechanic complete a check engine light inspection, they will be able to download the code and determine the source of the leak. In most cases, it’s an EVAP purge solenoid that is faulty.
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Is this car typically a great running car? And what is usually the main issue with this particular car make and model?
ANSWER : In evaluating the wisdom of buying a particular model of car (used or new), consult the database of the National Highway Traffic Safety Administration, NHTSA. The NHTSA database contains model specific consumer complaints, official recalls and factory service bulletins searchable by individual make, model, and model year. I encourage you to go to the NHTSA website and enter "1998 Mercedes Benz C230" into the search dialog box and simply review the existing reports. For the 1998 Mercedes Benz C230, I see that there is 1 recall, 2 investigations, 56 consumer complaints (that’s a relatively small number), and 10 Technical Service Bulletins (discussing post production problems unique to the vehicle). If you carefully review these reports you will gain an excellent overview of what has been experienced by other owners insofar as faults in the particular make, model and year you are interested in. I would post the text of the reports here, but they are detailed and voluminous so it will be more practical for you to view them online (it is free). An additional resource, "Consumer Reports", publishes system-by-system vehicle reliability data for all years, makes, and models. This data is available free in the library, or on-line if you are a paid subscriber. That reliability data will give you an excellent indication of the relative likelihood (probability) that key systems on the model (and year) of interest to you will fail at greater, or lesser, frequency compared to those rates reported for other vehicles. Obviously, what you want to be looking for in the "Consumer Reports" database is an indication that the vehicle "make and model year" of interest to you is not a "lemon" insofar as reliability. Finally, to protect yourself in any used car transaction, you should request a pre-purchase vehicle inspection. That inspection, carried out by a certified Mechanic, dispatched to your location by YourMechanic, will give you very specific data regarding any current problems with the actual car you want to buy. If you are unable to access any of these resources, or desire data of a different type, please do not hesitate for a moment to re-contact YourMechanic and we will assist you further in your attempts to make a wise used vehicle purchase.
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