Engine idle fluctuates
Rpm fluctuating when engine is at operating temperature, the problem happend after i changed the fuil filter, spark plugs and also the radtor hoes. I changed out the map sensor a few hours ago but still having the problem.
Please help me
My car has 1800 miles. Also has an automatic transmission.
Experienced mechanics share their insights in answering this question :
This may be a result of a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since this valve is controlled by the vehicle’s computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your idle air control valve.
How to Identify and Fix Common car Problems ?
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Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.
If your RPM starts fluctuating, there might be issues with the engine`s combustion process, a communication gap between the IAC and the ECU, or it can be a worn-out spark plug.
Causes of a rough idle. Many different problems could result in a rough idle for your car or truck, including: dirty fuel injectors, clogged air filters, bad spark plugs, and a variety of exhaust system issues.
Idle speed can also fluctuate when the engine is not running the right amount Fuel type receives. This can happen if a pressure valve of the high-pressure pump or the fuel pressure regulator is defective. A clogged fuel filter can also reduce fuel flow.
How to fix it? Cleaning or replacing the fuel filter and adding a fuel injector cleaning treatment to the fuel tank should take care of clogged fuel injectors. If the rough idle persists, it`s time to take your car to an auto repair shop.
Replace the sensor with a compatible one and correctly install the crankshaft position sensor to ensure that the engine runs optimally and safely. A qualified technician can prevent further issues with RPM fluctuations while driving by installing the sensor correctly.
Oxygen (O2) sensor
An oxygen sensor monitors and analyzes the amount of oxygen in a vehicle`s exhaust system after combustion. A dirty, damaged or malfunctioning O2 sensor (or sensors) affects the air/fuel mixture, causing the engine to idle rough.
Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle. A mass airflow sensor detects the amount of air coming into the fuel injection system and sends that information to the vehicle`s computer.
Your tachometer needle will bounce up and down if your engine has a vacuum leak. The vacuum created in the combustion chamber is used as a power source, and, as such, it is routed through the engine to various locations using vacuum hoses. Over time, Collins Auto Care advises that these hoses can start to leak.
If the alternator is dying and the battery isn`t fully charged you can expect all kinds of weird electrical problems to happen. The alternator output will fluctuate with changing RPM.
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Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
Engine idle fluctuates
This may need to have the throttle stop screw adjusted. The throttle stop screw’s primary function is to prevent the throttle blade from closing too far and getting wedged/stuck in the throttle bore. However, it serves as a secondary function to adjust the minimum air setting. The “minimum air setting” is what is used to describe the amount of air that is allowed to enter the engine thru a “closed” throttle. Because the throttle valve cannot be allowed to completely close (because this would result in it getting wedged/stuck closed in the throttle bore), some air will always be allowed to enter the engine around the throttle valve. On a 100% factory stock engine, you should never need to adjust the throttle stop screw. But there are times when the adjustment of this screw is necessary. One example of this is when the engine is modified, or a different throttle body is being used than what originally came with the engine. Larger displacement engines require more air to maintain a set idle speed. Aftermarket camshafts with lots of duration or lots of overlap tend to lower the amount of vacuum an engine can generate at idle. Lower vacuum levels translate to less pressure differential between the intake manifold and outside (ambient) air. This means there isn’t as much pressure difference to force air into the engine around the throttle blade or thru the IAC passage at idle. Either the IAC needs to open up or the throttle blade must be opened more to allow more air to enter the engine. Engines that have higher compression or are new/rebuilt can have higher internal loads/friction which can also result in a drop of idle vacuum levels. In short, any condition that increases load on the engine will result in the vacuum level to drop at idle, which will require the IAC or throttle blade to be opened up to compensate.
High idling, jumping while idling, idle air control valve code
Hi there. This can be caused by the issues that you mentioned or a number of other things. You need to make sure all of the connectors are making good contact. I would then need to know what codes are in the computer to know if this is a circuit issue or not. Most of the time, it is not the circuit but instead a vacuum leak.
If there is a vacuum leak, then the vehicle will act like this and the computer cannot control the idle. Most of the time it is a bad hose or an EGR valve that is stuck open. That is the most common cause for this. I typically remove the EGR to check it to feel the diaphragm on the bottom of it to see if it is moving correctly. If you need to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose and repair your car’s idling issue.
Engine hunts/stalls at idle.
Hi there. The issue seems to be a vacuum leak on the engine. Get a stethoscope that is made for automotive vehicles and listen for a hissing noise around the intake gasket or the intake hosing to the throttle valve. If there is a hissing noise, then the gasket or hoses are in need of replacement. A vacuum leak on the engine will cause the idle to hunt when operating. If you need further assistance with your engine idle hunting, then seek out a professional, such as one from Your Mechanic, to help you.
My 2003 Mazda Tribute stalls in gear, no power, rough idle, not the plugs, oil fouled black, clean maf and idle air valve
Hello. I would start by scanning the vehicle for codes and checking to see if all of the sensors are reading correctly. If everything looks good then chances are it needs a new computer. I have seen the computers fail on these vehicles over and over again causing the ignition circuits to not work correctly which causes the vehicle to run just like this. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to you to [diagnose why the vehicle is running like this] https://www.yourmechanic.com/services/car-idle-is-rough-inspection
Can front wheel drive car engine power rear wheel drive
Anything is possible with enough engineering. The changes you are looking at would take major structural changes and would definitely not be an easy job. You could possibly consult a manufacturing engineer to get more details on how this could actually be carried out and whether it would be feasible.
Engine idles in cold temps, sometimes in warm, idles in neutral and engine sometimes shuts of when stopping
You could try cleaning the throttle body and idle control valve. If the engine has a vacuum leak, then fix the leak. An idle of around 900 RPMs is about normal for most manual transmission vehicles and you may have other problems causing the engine to stall.
If you need help then have a qualified mechanic run a diagnostic inspection and recommend the best path to repair.
1998 Lexus es300. Can no engine compression mean bad computer and not engine replacement?
An engine computer cannot control, or affect, "basic" engine mechanical compression, that is the level of cylinder compression measured in a static test. Even in the complete absence of any engine computer, the basic specified compression of an engine will exist. If the engine doesn’t have the minimum specified compression, then the engine is mechanically broken. If the timing belt on the engine is in the correct position, the SOLE determinants of engine compression, during the typical static test, are: 1) the condition of the cylinder walls and the piston rings; 2) the condition of the engine valves and valve train; and 3) the condition of the head gasket. Consequently, if the engine has no, or little, compression during a test with the throttle held open, there is a mechanical problem with the engine, not an electrical problem. I would first check to be sure the timing belt has not slipped; that fault alone can ruin compression. If the timing belt has not slipped, and you desire a run down of your options to get this resolved, please request a rough engine operation diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.
How do you replace the rear & side engine mounts without lifting out the engine? & how do you lift the engine out?
Hi…thank you for your questions. If required in the application, a portable engine support bar is used to support an engine during mount replacement. The support bar has lifting capability as well so that the mount can be unloaded and removed. If a particular repair application requires a "crane" (complete engine removal for instance), such are portable these days in any event. With regard to the exhaust system repair, mechanics use ramps to gain access. Six ton portable jack stands will safely support a car two feet into the air which provides more than enough access to repair or replace any exhaust system component. If you desire replacement of the mounts, please refer to YourMechanic’s motor mount replacement service page. For exhaust leaks, please use the exhaust system inspection/repair page page. Once on each of those service pages, if you click on "Get a Quote" and enter your vehicle information (year, make, model) you can obtain cost info and schedule the service. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.