Why Does My Car Rpm Go Up And Down

  • Why Does My Car Rpm Go Up And DownIt could be a bad ignition coil or spark plug. A malfunctioning cooling system can reduce the efficiency of your engine, leading to loss of power and rpm. There are a few things that could be causing this problem: 1. There are many reasons why the RPMs might be running high. Summary Your vehicle might develop issues over time. Traveling at 40mph (or any speed in general), RPM's at around 1,200 on a flat/straight road. Sign in to reply jroemen on November 03, 2011. Summary Your vehicle might. It also drastically increases the rate at which your transmission becomes worn out. A knocking is usually the result of bad starts, a loose ball joint, or a bad bushing Read more It turns over but wont start Hi there. Some possible causes why a car shakes when AC is on: Faulty AC Compressor. When your RPM goes up, and the car does not accelerate, it means there is a fault with one or more components of the vehicle. Malfunctioning Mass Airflow Sensor. Remove the ignition caps (or coils, as modern cars often have coil-on-plug systems) and proceed to replace the spark plugs. If you notice your car's RPMs fluctuating, the first thing you should do is check the air filter. This can be caused by a bad fuel filter, fuel pump, or fuel injector. Car RPM fluctuates while idle: 6 causes and solutions!. Why do my rpms go up and down when idling? Among the potential underlying causes are vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor. A failing AC compressor, Bad belt, or overfilled AC system are also the reasons why your car RPM goes up and down while AC is on. RPM go up and down Peter Finn the Car Doctor 273K subscribers Join Subscribe 3. I was thinking maybe it's the camshaft&mass air flow. This is because the idle control unit controls the engine’s RPM so that it remains at a low level. Spark plugs progressively deteriorate with use and must be changed to maintain appropriate operation. If your car usually idles at 800 rpm, it should be about 50-100 RPMs within that. A malfunctioned RPM might make shifting a hurdle. RPM Fluctuates While Accelerating: Causes, Symptoms and Costs">RPM Fluctuates While Accelerating: Causes, Symptoms and Costs. What to do when your BMW Revvs on its own – A Better BMW. It measures the rate of airflow in your fuel. RPM go up and down - YouTube How to repair Bad Idle Speed problem in car. my vehicle was idling slightly ">I was stopped at a red light, my vehicle was idling slightly. The flow of air might have been compromised due to a leak. What causes RPM to fluctuate while driving? Worn-off spark plugs or clogs in the fuel delivery system are the most common reasons behind the RPMs fluctuating while driving. The job of the transmission fluid is to aid in transferring power to the wheels. The firing sequence is very important, and if you notice the RPM going up and then going down on a repeating pattern, it could be caused by defective spark plugs. There are a few things that you can do to try and unclog your fuel injector. If it occurs, your auto revs at high RPM due to the torque converter or gearbox band slippage. It might be blocked; you will need to take it to the mechanic. Your RPM can go up and down due to problems with your spark plugs, transmission problems, or a vacuum leak. Causes of RPM Idling Up and Down If you have driven a vehicle for a certain amount of time, you will become familiar with how it handles and how it feels under certain conditions. In most cases, you can easily stop this from happening just by simply cleaning your IAC. If your car's fuel pressure is too low, it can cause the RPM to fluctuate. Reasons Why Your Car Won’t Accelerate but RPM Goes Up 1. A defective catalytic converter can also cause your engine to lose power and rpm. A clogged fuel filter filled with dirt and dust won’t make enough room for air into the engine. Broken or wear out engine mounts, bad air conditioner compressor, and defective fuel injector are the main causes why a car shakes when AC is on. Here are some possible causes of your vehicle RPM going up and down at idle: 1. What Causes Fluctuating RPM? Now that we know what RPM is and why it matters let's discuss the reasons why your RPM goes up and down while parked. Air Leak In The Intake Channel. An RPM going up and down at idle can also be because of a defective Mass Airflow Sensor (MAS). Here are some of the most common reasons why your car's RPM drops: A broken or clogged fuel injector can cause your car's engine to lose power and rpm. What Causes Fluctuating RPM? Now that we know what RPM is and why it matters let's discuss the reasons why your RPM goes up and down while parked. RPM Going Up and Down at Idle: Causes & Solution (2022). Detach the battery and permit the car to cool down. It can also happen when the spark plugs are dirty or if there is a vacuum leak that causes misfires. Additionally, a dysfunctional idle air control valve or a faulty crankshaft position sensor. Poor car maintenance resulting in clogged oil, fuel, and air filters normally causes this. There is a problem with the engine’s air intake. How do you fix RPM fluctuations?. If the clutch is worn out and is slipping while driving, then it can cause an increase of the RPM of your car even though you are on a constant speed and not accelerating, burning more fuel. The leak could be sourced at the seal, or more often, in one of the attached hoses. Hence they disengage the gears and put it in Neutral. What Causes Rpms to Fluctuate While Driving?. And the only reason i probably can hear it is because I have a magnaflow exhaust, which is probably more audible. It usually happens when the car is unable to. You would have to look at a wiring diagram and see where the circuits cross on the power or ground side. You can fix this problem by replacing your. This can be caused by a dirty air filter, bad spark plugs, or a clogged fuel filter. The problem might also be from the timing or floating of the valve. RPM Fluctuation While Driving. So i noticed a very unusual event that my car makes when going down a hill. Basically, when an engine surges, you notice your car speeding up and slowing down even while you keep the accelerator steady. RPM fluctuation while driving is a typical sign of filthy or worn-out spark plugs because unclean or worn spark plugs are unable to provide the right spark required to ignite the gasoline at the proper. So, if you don't want to face RPM fluctuation just because of a clogged air filter, ensure to clean or change the air filter religiously. Worn-out or dirty spark coils or plugs. RPM will also go up and down as I'm accelerating. check air filter and spark plugs first to make sure there clean, if there both fine then I'd look in the direction of clogged or dirty fuel system and injectors if there's no CEL light on the dash as this would restrict the fuel getting to the engine but not completely stop it from starting which may explain the rough idle as. Transmission Fluid Transmission fluid is exclusive to automatic vehicles. This can cause the vehicle's RPM to go up and down without prior notice. If the knocking only occurs when the vehicle is moving then you either have an engine mount issue or a suspension problem. It also drastically increases the rate at which your transmission becomes worn out. When the driver shifts to a higher gear, the engine rotates a larger cogwheel. It can also be caused by spark issues from bad spark plugs or ignition coils. This can cause the vehicle’s RPM to go up and down without prior notice. Yes, a crack in a hose or any leak in any part of the vacuum system can and will cause engine idle problems. If your car has a defective idle control unit, it will cause the RPM to go up and down while parked. Different indications of a terrible spark plug incorporate abundance vibration, helpless speed increase, awful efficiency, difficulty to begin, engine failing, and solid fuel smell from the car’s fumes. The first thing to do is to check for bad spark plugs. Here are some possible reasons your RPM is going up and down while driving: Worn-out spark plugs. This is because the idle control unit controls the engine’s RPM so that it remains at a low level. Summary Your vehicle might develop issues over time. Power loss, rough idling, hissing car sound, low fuel efficiency, and car stalling are signs of a vacuum leak. If it's something like worn-out spark plugs, it will be a quick fix. I was told it could be a transmission problem. Lastly, your RPM may fluctuate due to a transmission leak. Mark helpful 510 corvairer answered 10 years ago also, could be something fuel related such as a bad oxygen sensor, fuel filter, or MAP sensor. This is because the engine isn't getting enough fuel to run smoothly. Start by parking your car and switching off the motor. The first thing to do is to check for bad spark plugs. It could be an instrument cluster problem, but it sounds like a bad ground, another circuit (brake light, heater circuit) is feeding back into the speedometer and making it pulse. If you do it cold and fill it up, it will be over full when completely warmed up. Why do my rpms go up when going down hill? – Sage. There are many reasons why the RPMs might be running high. Worn-out spark plugs cause the RPM in most older cars to fluctuate. It goes up and down. If your RPM goes up and down while accelerating it’s likely due to worn-out spark plugs, however, here are some other common causes: Bad Idle Air Control Valve When your RPM fluctuates while accelerating, it’s generally due to a problem with the idle air control valve, or IAC, in your automobile. Rpm goes up and down. Leaking, sticky or partially restricted fuel injector (s) A faulty emission control system. Low Transmission Fluid (Automatic Transmission) A low transmission fluid level is one of the reasons why your car won’t accelerate but rpm goes up. Why Does My RPM Go Up & Down?. When the injector is clogged, it can’t deliver the right amount of fuel to the engine. RPM Fluctuation While Driving: Why RPMs Going Up and Down?. Other times it can be a problem with a cracked intake tube. While going along on the highway, the RPM and acceleration should be stable and constant, not fluctuating. If your plug is damaged it might cause your. The IAC in your car can often not work properly because of the buildup of carbon in the IAC. RPM Fluctuation While Driving: Why RPMs Going Up and Down?">RPM Fluctuation While Driving: Why RPMs Going Up and Down?. If your RPMs are consistently going up and down, it could be a sign that something is wrong with your engine. It primarily happens because the wrong valve timings affect the air mixture and the engine’s capability to create power. There are a few reasons why your car might be revving up and down while idling. You can also test your fuel pressure or try to do a compression test. Vacuum Leaks; Dirty or Faulty Idle Air Control Valve; Malfunctioning Mass Airflow Sensor; Failing Alternator. So, if you don’t want to face RPM fluctuation just because of a clogged air filter, ensure to clean or change the air filter religiously. If the engine is older or has higher miles on it, the typical culprits will be dirty sensors and carbon deposits on engine head components. Causes of RPM Fluctuation While Driving Many RPM fluctuations are caused by transmission problems. What Can You Do to Fix Fluctuating RPM? Now that we know what causes fluctuating RPM let's discuss what you can do to fix it. RPM going up and down — causes and fix. Lastly, engine misfires can come from a loss of vacuum coming from the intake system. When the crankshaft position sensor wears down or becomes damaged, it can cause your RPMs to fluctuate. Then drop it from D into 3 and watch your tach. The perfect shift lies slightly before the indicator reaches the red zone. Why Does My Rpm Drop To Zero While Driving? (Solved!)">Why Does My Rpm Drop To Zero While Driving? (Solved!). If you feel that your car is hesitating to move, your accelerator pedal sensor could be failing. RPM go up and down Peter Finn the Car Doctor 273K subscribers Join Subscribe. If it doesn't register on your boost gauge and valve overlap isn't a problem, you have a major leak. Someone said it might be a clogged egr. Why Does My RPM Go Up and Down While Parked?. If the engine is revving up and down, it might be because of a problem with the ignition system. The higher the RPM, the more power the engine generates, and the faster the car can go. Your vehicle and transmission must be fully warmed up when topping off the transmission. If Read more Engine not getting fuel. You may also experience vibrations and have trouble starting your car. If the IAC motor’s vacuum port is leaking, this can be another cause of high engine idling. Also, slight chance your a/c compressor could be cycling quickly if the charge is low 17 people found this helpful. One possibility is that there is something wrong with the engine. Yesterday after I put a full tank of gas at Chevron in my 1994 Nissan Quest the car started to jerk around and shake. It can lead to surging and stalling and cause the RPMs to go up and down. If your RPM goes up and down while accelerating it's likely due to worn-out spark plugs, however, here are some other common causes: Bad Idle Air Control Valve When your RPM fluctuates while accelerating, it's generally due to a problem with the idle air control valve, or IAC, in your automobile. The firing sequence is very important, and if you notice the RPM going up and then going down on a repeating pattern, it could be caused by defective spark plugs. It's also caused by bad shift solenoids, a worn clutch, a damaged gearbox or various drivetrain problems. If your car has a defective idle control unit, it will cause the RPM to go up and down while parked. There are many reasons why a car would misfire. When this fault appears, there are a number of components or systems you may want to look into first: Vacuum leaks at the intake manifold or vacuum hoses. You might also notice other symptoms, like a loss of power or a rough idle. Why Does My Car RPM Go Up and Down While Parked?">Why Does My Car RPM Go Up and Down While Parked?. It could be something as simple as a dirty air filter, or it could be a more serious issue like a faulty fuel pump. Share Improve this answer Follow answered Jan 10, 2013 at 22:29 Chris Porter 111 3 Add a comment 1. Worn-out spark plugs can cause misfires to occur within. Why Does My RPM Go Up And Down While Parked? Your RPM may go up and down while parked due to several potential underlying causes, including vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle. If there is any codes or a light showing its going to be a sensor picking something up in or around the engine like the crank sensor or possibly timing related depending on the. If your accelerating won't go past 40 mph, then there might be a problem with your exhaust pipe. The most common reason why your car activates limp mode is that there is something wrong with the turbo charge pressure. There are many reasons why rpms may fluctuate while driving. Your RPM can go up and down due to problems with your spark plugs, transmission problems, or a vacuum leak. Sandy answered 8 years ago 43 people found this helpful. An engine vacuum leak is another probable cause of a vehicle’s RPM fluctuation. You need to get the clutch tightened by a mechanic. The issue could be a dirty air filter. Worn Spark Plugs Or Spark Plug Wires; 2. Reasons Your Car Won't Accelerate But RPMs Go Up When a gas pedal is pushed down, the car is meant to accelerate. If your RPM goes up and down while accelerating, it’s possibly due to transmission gear slippage or a bad MAF sensor. The region ought to have satisfactory room and lighting. In such a case, it is advised to pull over immediately and call a mechanic, since a bad pedal signal can be. Thats why i believe its something to do with the ignition of a cylinder. Confirm if the pressure on the turbo is rising or the vehicle’s system is not receiving the required boost pressure. A clogged fuel filter filled with dirt and dust won't make enough room for air into the engine. Reasons Why Your Car Won't Accelerate but RPM Goes Up 1. What Causes Rough Idle When AC Is On? Sometimes your car can get rough idle if you turn the AC on, and car owners often face this problem. Car Won't Accelerate but RPM Goes Up (Causes & Fix). Start by parking your car and switching off the motor. Reply Save Like P Pretty in red · #5 · Apr 25, 2011. This can cause the vehicle’s RPM to go up and down without prior notice. When you stomp on the accelerator, the engine starts to rotate faster, this increases the RPMs. There are a few reasons why your RPM might be going up and down at idle. Car Revs Up and Down Causes As you’re driving along the highway, you can feel as your car maintains speed. When this fault appears, there are a number of components or systems you may want to look into first: Vacuum leaks at. Everything you describe sounds normal except for the hesitation which might mean you need a tune up. Different indications of a terrible spark plug incorporate abundance vibration, helpless. RPM fluctuation while driving is a typical sign of filthy or worn-out spark plugs because unclean or worn spark plugs are unable to provide the right spark required to. When your RPM goes up, and the car does not accelerate, it means there is a fault with one or more components of the vehicle. It could also be a bad control module or wiring issue. Second, it can be due to faulty torque converters. My rpms are going high and my mph take a minute to go higher on my …. If your RPM goes up and down while accelerating, it's possibly due to transmission gear slippage or a bad MAF sensor. How to repair Bad Idle Speed problem in car. Power brakes work off engine vacuum and can sometimes cause a slight variation in engine RPM due to the small, temporary vacuum drop in the engine when you hit the brakes. When a car down shifts to a lower gear, the RPM's will shoot up. Also at times it feels like it's skipping a little. refill the gas tank and if it seems better than get some additive that removes water 46 people found this helpful. This is because the idle control unit controls the engine's RPM so that it remains at a low level. RPM fluctuation while driving is a typical sign of filthy or worn-out spark plugs because unclean or worn spark plugs are unable to provide the right spark required to ignite the gasoline at the proper moment. It can also happen when the spark plugs are dirty or if there is. You may notice the tachometer fluctuating, for example, from 1500 to 2000 rpm. If it doesn't, it could mean the transmission is slipping, or you have a bad torque converter. Why Does My Car RPM Go Up and Down While Parked?. Here are some possible causes of your vehicle RPM going up and down at idle: 1. Rpms to Fluctuate While Driving?. Mark helpful 40 kmp1123 answered 6 years ago. Below we look at why your car RPM can go up and down when you’re parked and whether the fix is expensive or not. Some people have a misconception that due to more RPM, the engine consumes more fuel. A malfunctioning cooling system can reduce the efficiency of your engine, leading to loss. 6 Common Causes of RPM Fluctuation While Driving. The most common reason why your car engine is sputtering is because of an issue with the fuel system. Plugs are responsible for the creation of the spark that ignites the fuel in the engine. There can be many causes for engine surge, and they may vary from one car model to the next. Why Your Car Engine Is Sputtering And How To Fix It">8 Reasons Why Your Car Engine Is Sputtering And How To Fix It. Lastly, your RPM may fluctuate due to a transmission leak. Dirty or Faulty Idle Air Control Valve. It's usually a very small RPM change, but it can sometimes be enough of a variation to notice. It also drastically increases the rate at which your transmission becomes worn out. The most common causes of a BMW revving on its own are: 1) a bad idle control valve, 2) sticky throttle cable, 3) bad throttle position sensor/throttle plate issue, 4) floormat pushing the accelerator, or 5) cracked vacuum line. 5 Reasons Car Won't Accelerate but RPMs Go Up Automatic. If the idle speed is set too high or too low, it can cause the RPMs to fluctuate. However, no lightsIt just idles high then low then high again. Engine stalling and rough idling are two additional typical signs of a faulty IAC. An interruption of the airflow in the exhaust system or your car’s intake manifold causes a vacuum leak. A uneven idle on a F-150 can be a symptom of a variety of engine issues such as vacuum leaks, failed or dirty sensors or worn engine components. I think what is happening is that your car is just down shifting when you are applying the brakes. In some cases, the crankshaft position sensor may send the wrong engine speed signal to the tachometer. I just happened to noticed due to the fact i started taking a new way to work because the traffic is less and it has a few down hill slopes. Sometimes, you might feel it speeding up or slowing down on its own, which could come from a number of causes. 4 Answers F_O_R answered 6 years ago When you push on the gas the RPM's are supposed to go up. Another possibility is that there is a problem with the fuel system. This increases the speed of the car and reduces the number of RPMs. Why Are My Rpms Jumping Up And Down At Idle? 1. Car Won't Accelerate But RPMs Go Up: Causes & Fixes. RPM Fluctuates While Accelerating: Throttle Pedal Position Sensor Being Faulty. Pay attention when filling it up as this is very important. The defective idle control unit will cause the engine to overheat and eventually fail. While the car shakes or vibrates, you can hear the noise at close notice. If it occurs, your auto revs at high RPM due to the torque converter or gearbox band slippage. Lastly, your RPM may fluctuate due to a transmission leak. Lesser likely causes are a clogged throttle body or a. If your car has a defective idle control unit, it will cause the RPM to go up and down while parked. If your RPM fluctuates while accelerating, it could be because your spark plugs have gone bad on you. It is a pulsing sound comming from the exhhaust and can also feel. Why Does My RPM Go Up and Down While Parked? Causes & Fixes!">Why Does My RPM Go Up and Down While Parked? Causes & Fixes!. Additionally, a dysfunctional idle air control valve or a faulty crankshaft position sensor can also lead to RPM fluctuations. Older vehicles such as your Suburban tend to be a little easier to diagnose. It does stutter when I pull off. First, it can be that your fuel is making its way to your engine correctly. If it occurs, your auto revs at high RPM due to the torque converter or gearbox band slippage. Then when looking at the rpms you can see them pulsing too. There can be many causes for engine surge, and they may vary from one car model to the next. Causes of RPM Fluctuation While Driving Many RPM fluctuations are caused by transmission problems. A defective catalytic converter can also cause your engine to lose power and rpm. What causes RPM to fluctuate while driving? Worn-off spark plugs or clogs in the fuel delivery system are the most common reasons behind the RPMs fluctuating while driving. While going along on. Q: Car rpm goes up and downstuttersIdk what's wrong. Rpm goes up and down stutters. Most often, this is because the boost pressure is too high. Low Transmission Fluid (Automatic Transmission) A low transmission fluid level is one of the reasons why your car won't accelerate but rpm goes up. Air Leak In The Intake Channel Confirm if the pressure on the turbo is rising or the. Here are some possible causes of your vehicle RPM going up and down at idle: 1. Assuming the spark plug is grimy or exhausted, the RPM will drop or flood. First, look at all of the couplers from the turbo to the TB elbow and make sure they're all secure and that a tennis-ball-sized rock didn't go through your intercooler. Therefore, your vehicle’s RPM will start going up and down abruptly. Why a car won't accelerate past 40. Either transmission is slipping or engine has an intermittent misfire issue. My Accord started doing the rpm thing, it will rev up and down at idle but it stops doing it if you give it a bit of gas or simply put it in gear. If you have a bad IAC you might see the RPM jump up and down when you accelerate. Malfunctioning throttle pedal position sensor. Car Revs Up and Down Causes As you're driving along the highway, you can feel as your car maintains speed. One reason could be that the car is not running smoothly and the engine is not getting the right amount of fuel. The car activates limp mode to prevent serious engine damage from occurring. The best spot to make car repairs and substitutions are carports. One thing you can try is to use a fuel injector cleaner. Is it normal for RPM to fluctuate at idle?. One possibility is that there is something wrong with your engine. If you suspect that your. It’s also caused by bad shift solenoids, a worn clutch, a damaged gearbox or various drivetrain problems. At the same time, you may feel a soft and rhythmic jerking motion. It could mean that the; The clutch has been compromised The fuel system/injector is faulty Sensors are malfunctioning Damaged or disconnected transmission Clogged filters Why is my RPM high but slow acceleration?. If it doesn’t, it could mean the transmission is slipping, or you have a bad torque converter. -When you have a choice, buy American. When you are in the car next time, just put it in drive and go about 40 or so. Are there any codes stored in the ECM?. If you suspect a lack of fuel to be your issue you may very well be correct. Why Does My RPM Go Up And Down While Parked? Your RPM may go up and down while parked due to several potential underlying causes, including vacuum. What Causes Fluctuating RPM? Now that we know what RPM is and why it matters let's discuss the reasons why your RPM goes up and down while parked. Why Does My RPM Go Up And Down While Parked? Your RPM may go up and down while parked due to several potential underlying causes, including vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor. Another possibility is that there is something wrong with your ignition system. An overheating engine will often idle higher than normal, so be sure to check your engine temperature gauge. Your RPM may go up and down while parked due to several potential underlying causes, including vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor. Why Is The Car’s RPMs Jumping Up And Down At Idle? The jumping RPM of your vehicle is a result of a malfunction. It primarily happens because the wrong valve timings affect the air mixture and the. Therefore, your vehicle’s RPM will start going up and down abruptly. Usually, there are three leading causes behind car surging when accelerating. While these are not all possible causes, it’s a good start. Examine the inactive air control valve and discover the issue. Sometimes, you might feel it speeding up or slowing down on its own, which could come from a number of causes. If your car's fuel pressure is too low, it can cause the RPM to fluctuate. If it is over filled, greater pressures are exhibited and this will blow your seals out (front/rear). Why does my car rev up when i am going down hill while braking. Assuming the spark plug is grimy or exhausted, the RPM will drop or flood. The engine is not properly adjusted. The RPM goes up and down. Below we look at why your car RPM can go up and down when you’re parked and whether the fix is expensive or not. The more air that gets sucked into the engine though its vacuum system, the higher the engine's idle rpms will be. Remove the ignition caps (or coils, as modern cars often have coil-on-plug systems) and proceed to replace the spark plugs. If your plug is damaged it might cause your RPMs to run high. Another reason could be that the car is not in the correct gear. When your spark plugs are broken, they can’t ignite the fuel in the engine, which causes the RPM to go up and down. Air Leak In The Intake Channel Confirm if the pressure on the turbo is rising or the vehicle’s system is not receiving the required boost pressure. Why Does RPM Go Up and Down When Parked?. Air Leak In The Intake Channel Confirm if the pressure on the turbo is rising or the vehicle's system is not receiving the required boost pressure. Causes of RPM Idling Up and Down If you have driven a vehicle for a certain amount of time, you will become familiar with how it handles and how it feels under certain conditions. Here are some possible causes of your vehicle RPM going up and down at idle: 1. You brake system relies on vacuum and an idle speed that is affected by holding the brakes probably has a weak vacuum. RPM go up and down - YouTube How to repair Bad Idle Speed problem in car. Your RPM may go up and down while parked due to several potential underlying causes, including vacuum leaks, EGR system malfunctions, malfunctioning oxygen sensors, dirty fuel injectors, fuel pump malfunction, faulty spark plugs, a faulty mass airflow sensor, or a faulty throttle position sensor. Here are some of the most common reasons why your car's RPM drops: A broken or clogged fuel injector can cause your car's engine to lose power and rpm. If the transmission is engaged and the engine is connected to the wheels, as the wheels pick up more speed due to gravity, the engine RPM goes up during a downhill descend. The best thing you can do in this case is to keep an eye on the valve timing and adjust it when needed. Reasons Your Car Won’t Accelerate But RPMs Go Up When a gas pedal is pushed down, the car is meant to accelerate. RPM fluctuations while driving are often brought on by unclean or worn-out spark plugs. Any how if there is a large amount of water in the gas you may not see it until the tank is under half full Water floats on top of gas. You can get a cheap gauge at an auto part place that will quickly tell you if you are in spec. What Can You Do to Fix Fluctuating RPM? Now that we know what causes fluctuating RPM let's discuss what you can do to fix it. If your car's RPMs (revolutions per minute) are going up and down, it could be for a variety of reasons. And it jerks at times when pulling off. This causes the RPM to fluctuate when driving, accelerating, or while the engine is idling. Why Does My Car Rpm Go Up And Down.