Low RPM at idle? This is a common question that I always get from my channel and it seems that there are many vehicles that have the same issue. And why is that?
When a car’s idle have low rpm, for automotive mechanics that is called “surging”. In fact, whenever your car’s rpm goes up or down, than is also called surging.
So in this short post, I’ll discuss everything about this topic, why it occurs, its causes and some possible solutions. Read on to learn more.
What is Low RPM?
We always hear mechanics that cars should have proper or normal RPM to achieve optimum engine performance. But some engines do have tantrums and gives that surge from time to time.
And if yours is a total stubborn, your engine could be in low RPM all the time.
To understand this, you have to know how RPM works. RPM stands for “revolutions per minute”, which tells how many times the crankshaft revolved to produce engine power.
So when you accelerate, naturally the RPM increases. And when you slow down, the RPM decreases as well. RPM is also affected by some “loads” your car have like air conditioning, towing and many others.
This means that engine RPM changes depending on your car’s speed and load.
The normal RPM for most cars at idle is between 700 to 1000 RPM (1000 revolutions are denoted as 1X).
Anything above that range or below that range is called “car surging”. And most of the time, the common problem is engine surging low, meaning the engine has low rpm at idle speed.
So if your car has 600 or lower RPM, then your engine have issues that needs to be resolved.
Causes of Low RPM at Idle?
If your engine’s idle speed is not constant but is increasing or decreasing, then you have power surge issues. When this happens, the car’s usually vibrates or shakes, and some cases even stalls.
So what causes this problem? Let me give you some of the reasons why your engine has low RPM at idle.
Bad Fuel Injectors
Fuel injectors primary job is to inject mist of fuel to be mix with air for proper combustion. The mixture ratio should be perfect and balance. So fuel injectors does have a crucial role when it comes to power production.
A bad fuel injector (clogged or faulty) can’t spray the proper amount of fuel in a timely and adequate manner inside the piston chamber. This leads to surging or low RPM.
This also leads to bad fuel consumption as the injectors may inject more to compensate and achieve the proper air and fuel mixture.
To fix this, you need to fix or clean the injectors, replace them or just do a simple fuel injector relearn.
Faulty Engine Sensors
Your engine is packed with different sensors that affects it performance. This include oxygen sensors, coolant temperature sensor, oil pressure switch and many others.
What affects the RPM is called temperature sensor, which measures the temperature of the engine. A cold engine requires a thick mixture to start the car, while a heated engine requires regular mixing.
A bad temperature sensor can give wrong data to the computer which gives wrong mixture for the engine. And a wrong mixture can cause surging and low RPM.
Along with this, the mass air flow sensor measures the air that enters the engine. It gives data to the ECU which delivers the right mixture of air to be mixed with fuel.
A faulty MAF sensor will result to more fuel consumption and low RPM.
What to do? Identify which sensor in your engine is faulty and replace them as soon as possible.
Spark Plug
If you have a petrol engine, then it does have spark plugs, a crucial ignition component. To generate power, your engine needs sparks at the right time to help burn fuel and create ignition.
Otherwise, a bad spark plug leads to high fuel consumption, hard starting and of course, low RPM.
Your mechanic may suggest spark plug cleaning or replacement depending on your car’s mileage. So better include spark plugs on your car maintenance schedule.
Fuel System Issues
Aside from fuel injectors, some other components of the fuel system can also cause surging. This include a bad fuel pump and a dirty fuel filter.
Fuel pump’s job is to suck fuel from the tank and sends them into the mixing combustion chamber. A clogged fuel pump may seize to work resulting to erratic or low RPM due to improper fuel mixing.
On the other hand, fuel filter’s job is to filter any possible contamination before it goes into the engine. Like many other components, fuel filter will go dirty overtime and may clog the fuel flow.
What to do? You need to clean or replace the fuel pump so you’ll have proper fuel flow. Also, replace your old and dirty fuel filter as well.
Summary
There you have it. Above are some of the common causes of low RPM. There are other causes like damaged piston ring, worn valves, cracked head gasket, idle air control valve and many others.
So once your engine surges, take time to check every thing that I pointed here that could save you money and repair costs. Otherwise, it is no shame to go to your friendly mechanic for a routine car check.
