Everyone expects to hear the car engine revving up right before the transmission shifts, but not usually when it is in Park. If your car is revving in Park, it could be a sign that something is wrong. In this guide, we cover what it means if the car is revving by itself in Park and whether or not this is dangerous to the engine.
Why Is My Car Engine Revving In Park? (Common Causes + Fixes)
Why is my car revving in Park? For starters, the RPMs (revolutions per minute) typically remain stable when the car isn’t in motion. Whether it is in Park or idling while waiting, the RPMs shouldn’t rev. If they do, it’s an indication that something is wrong, typically nothing major, though. If caught early enough, simple maintenance could fix the problem.
If your car is revving in Park and Neutral, it could be due to one of the following issues.
Dirty Mass Air Flow Sensor
Why is my car revving high in Park? One of the most typical reasons is that the mass airflow sensor is dirty or contaminated. This sensor monitors how much air is moving through the intake to maintain the proper air-fuel ratio. If it can't get an accurate reading, the wrong amount of fuel could be injected to compensate, leading to a rough-running engine.
You may be able to clean the MAF sensor and restore the proper RPMs. If that doesn’t work, a replacement might be necessary.
Dirty/Sticking Throttle Body
If the car is revving on its own in Park, the throttle body could be sticking or contaminated. The throttle body is supposed to open or close based on the amount of throttle being received. It allows the appropriate amount of air into the engine.
If it sticks, it might open too much or remain closed, leading to erratic engine RPMs. It can also cause the idle speed to bounce around. There are special throttle body cleaners that can be used to remove contaminants. Other than that, it would need to be replaced.
Bad O2 Sensor
If the car is revving high in Park, there could be trouble with an O2 sensor. These sensors are found in the exhaust manifold, plus the catalytic converter to measure the amount of air coming from the exhaust. With this information, the computer can determine how to adjust the air-fuel ratio for better performance and efficiency.
When an oxygen sensor gets dirty or contaminated, the Check Engine Light might also come on. These aren’t normally expensive to replace, so it’s best to do it right away before it causes other issues.
Does your car shake when revving in Park? There could be a vacuum leak in one of the components. Because the engine works like a pump, sucking in air and compressing it, there can’t be any leaks. However, the lines are rubber, so they are prone to cracking after many miles of usage. As the air escapes, you are going to notice significant performance problems.
Replacing the vacuum hose isn't complicated or expensive, but it can be difficult figuring out where the leak is. You can try spraying some carb cleaner on the lines, or you might need to have a smoke test performed.
Plugged/Malfunctioning EGR Valve
If the car sounds like it’s revving in Park, the EGR valve could be to blame. The Exhaust Gas Recirculation system helps the vehicle pass emissions by sending the exhaust gases back into the engine for reuse. However, the carbon build-up can keep the valve from working correctly, leading to a rough idle or strange RPMs.
You can get a new EGR valve for a reasonable amount, and they aren't typically tough to install. This is one fix you don't want to wait on because it can cause rough performance and increase pollution to the environment.
Bad Throttle Body Valve Position Sensor
If the car engine is revving in Park, the throttle body valve position sensor could be the issue. Most modern cars use an electronic drive-by wiring system that has a throttle body valve position sensor meant to control when it opens or closes. If it becomes contaminated, it could send the wrong signals to the throttle body.
In some cases, you can replace just the sensor. However, many cars will require a new throttle body to fix the problem.
Frayed or Disconnected Wiring
If the car keeps revving in Park and you are having trouble finding the problem, consider checking the wiring that runs into the computer. Electrical wires are prone to breaking or fraying over time. When this occurs, the electrical signals aren’t transmitted correctly, leading to mixed messages that affect the engine performance.
In some cases, you might be able to replace the wiring or harness yourself. However, if you aren’t sure what you are working with, it’s best to trust a professional.
Faulty Car Computer
The worst-case scenario if the car is revving up and down in Park is a defective computer. The ECM, ECU, and PCM all impact how the car revs. If any one of these computer modules goes bad, the signals can get crossed, leading to multiple performance issues.
Sadly, these aren’t cheap fixes. You are going to pay a good amount to put a new computer in it, plus it needs to be reflashed by the dealer to work with your vehicle.
What Does Revving In Park Do To A Car?
Is revving a car in Park bad? Not necessarily. If you are purposely revving your car in Park to warm up the engine, it could be a beneficial practice. What you need to worry about is the revving car in Park that doesn’t happen because of your input. This situation is caused by a problem that needs to be dealt with before engine damage occurs.
Is revving your car in Park bad? Consider what’s happening with the fuel efficiency. You are using more fuel than you need to, allowing the engine to work harder without going anywhere. During this time, you are literally getting zero gallons per mile, which can be expensive if done frequently.
Common Car Revving Questions Answered
What causes a car to rev high while driving?
There’s likely a dirty sensor or failing mechanical part that may also turn on the Check Engine Light. You want to have it repaired before it creates further engine problems.
Is it good to rev your engine occasionally?
If you want to rev the engine in Park to warm it up, that’s a perfectly acceptable practice. Just be careful how high the revs go so you don’t cause unnecessary wear to the engine.
What happens if you rev your car too high?
The longer and harder you rev your engine, the more the throttle stays open. As the revs reach the red line on the tachometer, you can create permanent engine damage, which is a costly fix.
Why is my car revving up in Park? There’s probably a mechanical problem that you should deal with right away. In most cases, it’s simply the case of a contaminated sensor or part that can be cleaned, allowing you to get right back on the road.