RPM goes high while sitting still miss firing 02 Deville I think 4.8
Rpm goes high while sitting still or in park have to hit brake to bring it down miss firing
My car has 15000 miles.
My car has an automatic transmission.
Experienced mechanics share their insights in answering this question :
Hi…engine idle speed is controlled by an idle air control valve (IAC). A faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading to a higher than normal engine idle speed. The IAC valve itself can malfunction due to excessive carbon buildup in the intake manifold. Other possible causes of a high idle include vacuum leaks, a malfunctioning throttle and, rarely, a PCM/ECM malfunction. With regard to vacuum leaks, on a fuel injected engine a vacuum leak will cause a high engine idle as the engine’s oxygen sensor detect the extra oxygen entering the engine through the vacuum leak. The newly lean (too much air relative to fuel) status will result in the engine’s computer pumping in additional fuel, resulting in an abnormally high idle. A malfunctioning throttle system can cause both a high idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit. If you desire that this high idle problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine idle speed diagnostic – high idle and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
Faulty Fuse: In the majority of vehicles, engine idle speed is controlled via an idle control valve (ICV). A faulty or blown fuse in other electronically controlled systems can cause the Idle Air Control (IAC) motor to malfunction, leading to a higher than normal engine idle speed.
Multiple misfires can be caused by many reasons from a faulty ignition system, fuel system, or internal engine failure. The most common reason for this to happen is faulty or worn-out spark plug coil packs, especially if it`s been a while since you had a tune-up.
What does code P0300 mean? The P0300 engine code indicates a misfiring cylinder problem in your vehicle. The misfiring happens when insufficient fuel is burned or when the spark plug gets damaged. In addition, it can damage your car`s catalytic converter in extreme conditions.
P0300 Random, Multiple Misfire Detected means that your car`s computer (PCM) detected that there is a misfire in random or multiple cylinders. Code P0300 is often related to bad spark plugs or spark plug wires but could be caused by a number of issues relating to ignition and the air-to-fuel ratio in the cylinders.
High RPM – Idle speed is measured in revolutions per minute (RPM). For most 2 liter and below sized engines the vehicles, the standard idle speed should be around 750 RPM (when the engine is warm). If your car`s RPM is above 900 with a warm engine while idling, it is likely using too much fuel.
The engine`s oxygen sensor will detect the extra oxygen entering the engine via the vacuum leak which will alert the engine`s computer that the exhaust is running lean, which will prompt the computer to pump in additional fuel, resulting in an abnormally high idle.
Catalytic converter problems cause gas within your engine to heat up to the point that it actually ignites. This ignition is what causes the misfiring sensation – and that can destroy engine components. Anytime your vehicle misfires, you should have it checked out by a reputable service professional.
Worn or fouled spark plugs are one of the most common causes of engine misfires. These small but crucial components deliver the spark that ignites the fuel in your engine. If they`re not working properly, your engine won`t be firing on all cylinders.
The catalytic converter may certainly cause the P0300 random misfire code to show up due to the inability for the exhaust to properly breathe, which can cause un-burnt exhaust gases to reignite inside the catalytic converter. A clogged or failing catalytic converter can cause the vehicle to have poor fuel economy.
If the P0300 trouble code still persists, there could be a problem with the PCM. This may require replacing or reprogramming.
Typically, a random misfire shows up because of an issue with the ignition or fuel system, the ignition timing, or engine compression. Symptoms That May Show Up Along With P0300 Include: Rough running. Hard starting.
If everything is working as it`s supposed to, the engine idle speed should always remain the primary constant. However, over a period of time some mechanical components that monitor or control the flow of fuel into the fuel injector will become damaged and may contribute to increasing or decreasing engine idle speed.
An idle air control valve, also called an idle air sensor control motor, is an electrically operated valve that controls the amount of air that bypasses the throttle plate in cars with a fuel injection system [source: Autozone]. This causes the idling speed of the engine to change as needed.
your car surges and dies out: a faulty map sensor can cause engine rpm to fluctuate or surge, primarily at idle or low speeds. if you turn on the air conditioning or use the power steering when the happens, the engine can die out. it will usually restart, but this condition will worsen and can be dangerous.
A clogged or failed exhaust gas recirculation or crankcase ventilation valve or faulty oxygen sensor can send the wrong signals to the computer and cause misfires.
The type “A” misfire is the most serious condition and indicates impending catalyst damage. If detected, the Malfunction Indicator Lamp (MIL) may flash once per second to alert the driver that immediate service is required.
Driving with A Failed Catalytic Converter
If you`re noticing slow powertrain performance, reduced acceleration, a smell of rotten eggs or sulfur from the exhaust, dark exhaust smoke, or extreme heat from under the vehicle, these are symptoms of a clogged Catalytic Converter, and it should be replaced quickly.
Bad spark plugs or damaged exhaust valves can also destroy a catalytic converter. It is important to keep your engine and fuel injection system in good working condition.
High idle reduces soot in the exhaust which results from incomplete combustion at low engine revs. This is important because when diesel engines are operating at low RPMs, more soot is generated. That can fill up the diesel particulate filter (DPF) which has been installed on diesel engines since 2008.
Disconnect the idle air adjustment valve by locating and disengaging the electronic connector that holds it to the throttle body. Turn the idle screw to adjust the idle—turn the screw to the left to increase the RPM or to the right to lower it.
Disconnect the idle air adjustment valve by locating and disengaging the electronic connector that holds it to the throttle body. Turn the idle screw to adjust the idle—turn the screw to the left to increase the RPM or to the right to lower it.
High idle reduces soot in the exhaust which results from incomplete combustion at low engine revs. This is important because when diesel engines are operating at low RPMs, more soot is generated. That can fill up the diesel particulate filter (DPF) which has been installed on diesel engines since 2008.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
RPM goes high while sitting still miss firing 02 Deville I think 4.8
ANSWER : Hi…engine idle speed is controlled by an idle air control valve (IAC). A faulty or blown fuse in other electronically controlled systems can cause the IAC motor to malfunction, leading to a higher than normal engine idle speed. The IAC valve itself can malfunction due to excessive carbon buildup in the intake manifold. Other possible causes of a high idle include vacuum leaks, a malfunctioning throttle and, rarely, a PCM/ECM malfunction. With regard to vacuum leaks, on a fuel injected engine a vacuum leak will cause a high engine idle as the engine’s oxygen sensor detect the extra oxygen entering the engine through the vacuum leak. The newly lean (too much air relative to fuel) status will result in the engine’s computer pumping in additional fuel, resulting in an abnormally high idle. A malfunctioning throttle system can cause both a high idle as well as an engine stall. A dirty air intake or cracked air intake tube is often the culprit. If you desire that this high idle problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request an engine idle speed diagnostic – high idle and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
Car rpm goes up and down…stutters…Idk what’s wrong
ANSWER : An incomplete combustion in the engine will cause a sputter as can the ignition system. The fuel system, such as a blocked fuel injector may also cause the vehicle to sputter. While a sputtering engine may not seem like a major issue, it is a symptom of a bigger problem that will not self-correct and will eventually result in a much more expensive repair. The source of the sputter should be investigated by completing an engine is sputtering inspection and repaired as soon as possible.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
when i start my rav4(1997) the rpm goes high for about 5 min althought that wasnt occur before a period of time ,, what might be t
ANSWER : Hello, thank you for writing in. There are several causes for high idle after starting. The first thing to consider (although it has its limits), is that the engine does need more fuel when cold. This is why all cars have a higher idle after starting. Vacuum and a vacuum leak will have a huge effect on the RPMs. There are a few different tests you can do to find a leak if this is the case. Do a test that you can perform at home with the tools you have. Throttles and idle air control valves/solenoids are also largely responsible for the engine’s performance at idle. You will want to check these components next. It is a process of elimination to find what your issue may be. 2000 RPMs is too high for a starting idle, and there is likely a deeper issue going on.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
Idles between 500rpm and 1300 rpm. Main concern is low rpm. Belt or pulley chirping mainly at low rpm Drives perfect but Idles bad
ANSWER : Hello. From what you describe it would appear that your vehicle may have more than one issue.
Belt chirping is usually caused by a worn belt or tensioner. If either component wears out the belt may loosen and chirp when the engine is started, or cold.
The low rpm low quality idle can be caused by a few different things. I would look at the idle air control valve, as that is the component that maintains the vehicle idle, and at any vacuum hoses that may be cracked or damaged, and possibly leaking. This is more likely for older or high mileage vehicles.
If you’re unable to pinpoint the issue yourself, consider YourMechanic, as one of our mobile technicians will be able to come to your home or office to diagnose your starting issue firsthand and make the necessary repair to your car.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
Miss Fire Cylinder 4
ANSWER : Since you have a single cylinder misfire code, you’ll want to look at things that are specific to that cylinder. This includes items such as a bad fuel injector, spark plug or an engine mechanical problem (such as a failed valve). Unfortunately, what you describe does indeed sound like the recessed valve seat issue these engines are known for. When the seat recedes, it allows the exhaust valve to hang open. There is a technical service bulletin (TSB) # TSB 05-26-3 that describes the diagnostic steps to take in order to verify the issue. I recommend having a professional, such as one from YourMechanic, diagnose and repair your vehicle.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
I have a engine miss codes po174 po420 are on now I had code multiple cylinder miss fire. I changed spark plug wires and plugs l
ANSWER : Hi there. Your issue might be caused by a faulty O2 sensor. You might want to read this article about the P0174 OBD-II trouble code as it will show you possible causes, symptoms and solutions to resolve the problems.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
My 1997 infinity qx4 3300 will not shift into 3rd gear it just drives at a high RPM’s the faster I go the higher the RPM goes
ANSWER : Hi there. In most cases, when a transmission will not shift into higher gears, it’s due to transmission fluid problem; either it’s obstructed in the hydraulic lines, a torque converter issue or inner seal that is damaged. I’m not quite sure what you’re referring to in regards to "Put a new blocar in" – but, if the shifting issues occurred right after that service, it’s possible that is the source of your problem. You might want to have a professional mobile mechanic come to your location and complete a car is hard to shift inspection.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
High RPM’s when pressing brake
ANSWER : Hi There,
There are 3 sources of signals that are involved in up and down shifting points the computer arrives at to direct transmission shifting.
There are 3 sources of signals that are involved in up and down shifting points the computer arrives at to direct transmission shifting.
The Idle Air Control Valve. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal.
The Throttle Position Sensor. The throttle position sensor monitors the throttle position of the throttle plate inside the throttle body in relation to your foot position on the gas pedal. Based upon the inputs from the sensor reading your foot’s position on the pedal, the ECU then makes the direction to supply more or less fuel to the motor. When this sensor is not working properly, this can cause intermittent responses when pressing the gas pedal.
VSS speed sensing. The transmission speed sensor is a magnetic sensor that provides this information, allowing the transmission to shift smoothly. The sensor counts the internal number of revolutions of the transmission and transmits that information to the transmission control unit, where the data is used to determine the rotational speed. As the rotation increases, the control unit directs the changing of gears. When this is not working properly, this may cause the transmission to shift erratically or in some cases not at all.
I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle to determine what may be causing this.
Read Full Q/A … : RPM goes high while sitting still miss firing 02 Deville I think 4.8
