Last week I had a new car roll in the shop with a common problem on models older than ten years, an engine oil light on, but only when the car is idling. However, to my surprise, there was no car shaking when idling.
- Here’s why your oil warning light comes on when idling
- The oil light comes on when idling but goes away when I accelerate
- Check engine temperature – keep an eye on the engine overheating.
- What should you do if your oil pressure light comes on?
- How can you prevent this?
- In Summary
Here’s why your oil warning light comes on when idling
While the most apparent reason is a possible low engine oil level, that would not cause the warning to turn on only when the car is idling.
A more reasonable cause for an oil warning light while idling would be a loss of oil pressure due to a malfunctioning oil pressure sending unit or a bad sensor or pressure gauge.
Here is a list of the most common issues that can cause an oil light to turn on at idle or when stopped:
Faulty oil pressure gauge/ Bad sensor
The pressure may be optimal, but the oil pressure sensor or oil gauge is defective. As mentioned in the introduction of this post, I often see this problem with older cars. Usually, the check gauge light will also come on, indicating a problem with the vehicle.
After 10 – 15 years, your car is highly likely to develop all sorts of electrical issues, resulting in false readings.
I suggest taking your car to a repair shop or your local dealership and having a technician monitor your oil pressure using a mechanical oil pressure gauge. This will determine if there is a loss of oil pressure or not.
If there is no pressure loss, you will be happy to discover that your problem is a bad sensor and is not very costly to fix.
If the problem is not a bad sensor, it is probably caused by the worn crankshaft and camshaft bearings.
As the years go by, engine components become worn out, causing the oil to flow easier and a loss of pressure.
When accelerating, the flow increases, and the oil pressure builds up, causing your oil light to go off.
If you are lucky, it can get fixed with a new set of standard bearings if the crank journals are not worn out. Otherwise, it can be quite costly; therefore, I suggest having a mechanic do an oil pressure test first.
To better understand how oil goes in the engine, you can check this website.
What symptoms do worn engine bearings have?
As discussed, the main result of worn bearings is loss of pressure. This is usually indicated by your oil gauge or oil pressure light on the dashboard.
Another way to identify worn engine bearings is by paying close attention when you start the car. If the engine makes a knocking noise, it could indicate that your engine bearings need replacing.
However, there may be no noise if your bearings start getting worn out.
Not enough or old oil
I keep telling my clients that they must take proper care of their cars to avoid big bills. Having your oil change done regularly can prevent a lot of potential problems.
I recommend doing an oil change every 10-12 months or 8,000 – 10,000 miles, whichever comes first. Ensuring you have clean oil at all times will prolong the life of your engine.
Also, the oil change must be performed by a mechanic to ensure it is done correctly. Not adding enough oil can trigger your oil light to come on.
Wrong engine oil
I can’t stress enough how important it is to use the correct oil type. If you are doing the oil change yourself, read the car manual to ensure you use the right type.
A higher viscosity oil will be thicker, making it harder to flow through the engine during the winter, causing a pressure drop.
However, if you are sure you used the correct oil type, you should exclude this possibility.
Worn out oil pump
It is not very common, but I have seen it happen in the past. A faulty oil pump can sometimes result in oil flow dropping.
However, this would be the last thing to get checked as it can be a costly procedure.
Faulty pressure switch
It is possible that sometimes a bad oil pressure switch can send a false signal, indicating low oil pressure while it is not the case.
The oil light comes on when idling but goes away when I accelerate
This is an even more strange scenario, but there is an explanation for why this could happen.
The car is telling you that the oil pressure when idling is too low, but as soon as you hit the gas pedal, the pressure builds up, reaching the optimum level for running.
The things that can cause the oil light to come on just when the car is idling have been discussed before, but I’ll briefly touch upon them below:
Oil viscosity is too low
If the engine oil is old, poor quality, or the wrong type, it can cause the warning to come on just when idling.
Excessive bearings clearance
Worn bearings might allow the oil to flow easier, preventing the engine from reaching the optimum pressure to operate when idling.
Failing oil pump
A damaged oil pump can throw an oil warning light just when stationary with the engine running too. This happens as the pump does not manage to build enough oil pressure. If this is the case, the oil light will soon stay on permanently when driving too.
Check engine temperature – keep an eye on the engine overheating.
If the engine runs too hot, your oil will become thinner, preventing the pressure from building up. It is essential to notice when the light comes on.
Is it when you start the car in the morning, when the engine is cold, or after a long drive when it is hot. It can also indicate a low quality of the oil.
What should you do if your oil pressure light comes on?
If your oil warning light comes on, you should stop driving the car as soon as possible.
The next step is to contact a repair garage and either have it towed or drive there if the distance is not long.
Assuming the oil level is fine, have a mechanic check for an oil pressure drop by attaching a mechanical gauge to your engine.
If the mechanical gauge indicates a low oil pressure while idling and goes up when revving the car, you will most likely need to replace the bearings.
If the engine oil pressure is normal, the problem is a lousy sensor or a defective oil gauge which is the cheapest outcome for you.
If the oil pressure is nonexistent when the car is idling, your oil pump is faulty, and you will need to replace it with a new one.
Unfortunately, this can cost you between $600 -$800, depending on the make and model.
Oil is vital for your car engine to function correctly; therefore, running low on oil or using the wrong type of oil can cause irreversible damage to your engine.
How can you prevent this?
The easy way to prevent any issues with your car is by having it serviced by a competent mechanic on time. Using genuine parts approved by the manufacturer is also very important when servicing your vehicle.
If you purchased your car second-hand, make sure it has a full-service history and go through it to see if the previous owner maintained it to a high standard.
As car engine repairs will be costly, it is better to take every prevention method to avoid those hefty bills.
Also, I recommend addressing the problem as soon as possible; otherwise, things can get out of hand quickly.
While there can be multiple causes for an oil warning light at idle speed, I would start by first checking and replacing the easy parts, such as the pressure sensor.
My name is Jeffrey Williams and I have been a car mechanic for over 35 years. I am currently working NYC Auto Repair Shop, in New York City and recently developed a strong passion about blogging. I decided to put together this blog where I will try and answer the most commonly asked questions I get on a daily basis from my customers.