Why Is My Car Revving In Park? 7 Must-know Reasons

It can be a serious problem of engine breakdown when a car is revving by itself in the driving or idling state, potentially causing crashes or accidents.

So why is my car revving in park? Our article will present seven main causes behind your automobile’s sudden revving so that you can gain deeper insights into this matter and know how to solve it properly.

Why Is My Car Revving In Park? – 7 Main Factors

Why Is My Car Revving In Park

There are seven common reasons for your engine revving in park, including a dirty air flow sensor, a faulty throttle sensor, a damaged O2 sensor, vacuum leak, a plugged EGR valve, brittle wiring, and defective computer.

But before we dive deeply into causes, let’s explore what is “revving”? Revving is a slang term that means to increase car speed.

Sudden car revving on its own in park can grow into an enormous problem if left unattended.

This idle issue is normally boiled down to the wear of internal engines that help the vehicle maintain its steady velocity with common symptoms, such as thumping noise or car jerking.

Below are some popular factors behind this problem:

Dirty Mass Air Flow Sensor

Dirty Mass Air Flow Sensor

The dirty mass air flow sensor is one noticeable culprit behind the revving problem.

This sensor, which adheres to the automotive engine, is invented to sense the air mass flowing into the motor mechanism through the throttle part.

The data is subsequently delivered to the analytical system. Then, it will use programmed algorithms to estimate how much fuel is needed to create proper air in engine cylinders.

The MAF sensor can get dirty and clogged with dust and debris as time passes. This filthy build-up can ruin the mass air flow sensor, so incorrect air intake details are likely to appear.

Thankfully, you can use some exclusively designed cleaners, such as CRC spray, to clean the MAF sensor to restore its airflow reading ability.

It would be best if you also chose some cleansing tools that will not leave any film behind, which can wreak great havoc on the sensor.

Sticking Throttle Body

A dirty throttle body is another factor explaining the wonder: why is my engine revving in park? This device is created to control the fuel that goes into the engine.

It operates by opening or closing its valve to allow a specific portion of airflow into the engine.

Under the control of the MAF sensor, the throttle will open the way to let either a small amount of air or max airflow into the internal mechanism.

Like the mass air flow sensor, the throttle position sensor can become dirty due to crud over time.

As a result, its body ceases to perform the opening and closing functions normally, followed by the car’s erratic revving.

The good news is that you only need to clean the throttle valve so that the air can move freely into your vehicle engines. Below is our straightforward guide for you:

  • Prepare some necessary cleansing stuff, such as a clamp, an electric ratchet, a scrubby, a torque wrench, and an inspection mirror. Don’t forget glasses and gloves, as you may use some chemicals during the process
  • Disconnect the electrical connector for your safety
  • Remove the boot and four bolts attaching to the throttle body
  • Soak the throttle upside down in chemicals to take dust and debris off.
  • Please place it in a well-ventilated area to dry.
  • Put the throttle back into the engine system. Good luck!

Bad Oxygen Or O2 Sensor

Bad Oxygen Or O2 Sensor

The downgraded O2 sensor is also responsible. The oxygen sensor normally in the catalytic converter determines how much air output is from the exhaust pipe.

Afterward, it will send the data to the headquartered computer for analytical purposes, and the computer will subsequently adjust the air or fuel ratio to control the engine operating efficiently.

After a while, water droplets in the air passing over the oxygen sensor are likely to form carbon deposits and give rise to the rust phenomenon.

Consequently, it can no longer estimate the air outflow, which is why your engine revs when in park.

You can know whether your oxygen sensor gets broken or not by checking the engine light or using an OBD2 scanner to check engine codes.

The sole solution to this issue is to purchase a new O2 sensor, which may cost you under a hundred dollars.

Vacuum Leak

A vacuum leak is a plausible answer to the question: Why is my car revving high in the park? Each engine will take in the air through a vacuum and compress it into energy used for the wheels.

This vacuum will be used to power various systems under the hood, such as EVAP, brakes, or EGR.

A vacuum has a load of lines, as various systems are connected to just one engine. These hoses can crack and deteriorate over time.

Should this happen, a definite amount of air can escape via the cracked intake hoses, inducing the divergence between the true air ratio and what the MAF sensor estimates.

You can buy a new vacuum hose, which is quite cheap. However, tracking which line is responsible for the air leakage is a real challenge.

In this case, you must undertake a smoke test on each vacuum hose and identify idle speed changes.

Malfunctioning EGR Valve

Malfunctioning EGR Valve

This list of causes also entails a plugged Exhaust Gas Recirculation valve. This system was designed to help control the exhaust gasses emitted from the engine pipe, thereby safeguarding the environment.

But one acute limitation of this system is that carbon accumulation will likely come up after a short use time.

Its operation can be disrupted, as shown by the improper opening and closing function. Consequently, your car may rev in park wildly.

Fortunately, you can easily access and purchase components of the Exhaust Gas Recirculation valve. Replacing it is also simple and can be done by almost amateur mechanics.

Frayed Wiring

Under some circumstances, the revving matter is not attributed to a sensor, a throttle, or vacuum lines but to the disconnected drive-by cable system that acts as intermediate data transmission to your car’s computer.

When your automobile hasn’t been long repaired and maintained, electrical wires may corrode, which causes them to fray.

The data transmitted to the headquartered computer system may be faulty and inconsistent.

If you now have trouble with your car revving on its own in park, check the wiring connection in the nick of time.

This can be a recipe for more serious damage and wear in the future. Otherwise, it is strongly recommended that you try a new set of wires in case further problems stemming from the old wiring network arise.

Faulty Car Computer

Eventually, a bad computer may be in charge of your car revving in park. Some popular brand names, such as PCM, ECU, or ECM, are commonly referred to as the engine computer.

Despite different origins, they all have the same function to interpret provided information from many systems to keep the engine operating effectively.

For that reason, should a problem with the computer happen, it cannot summarize, analyze, proceed, and convert data into usable information.

Therefore, your automobile may have trouble running and revving up and down erratically, as it is under no control.

Unlike other problems, fixing a computer is not a simple task. Its parts are not always readily available, and the repair cost is beyond many people’s budgets.

Important Notes

  • This list is not exhaustive. There are also other causes explaining why your car is revving in park.
  • The car’s throttle body and associated sensors are common culprits behind this problem. So check these automotive parts first to save your time and effort.
  • An engine revving on its own in park is dangerous, as it can make your car suddenly raise the speed. Accidents or crashes on the road can follow.
  • Be careful when driving your potentially out-of-order transport for your and others’ safety. Go slowly, and pay attention to the road.
  • Once you find out something wrong with your car, get it solved at hand by checking its engines and systems at home. You should also have your rear wheel car towed to the service center workshop if it is unable to run.


All necessary information about the revving problem is provided in this helpful article.

After contemplating our post, we hope you will find your automobile’s exact problem and correctly answer a question: Why is my car revving in park?

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