The engine stalls at idle when warm. Causes and solutions

Engine stalls at idle when warm? If yes, sorry for that and we truly empathize with you for the situation, considering that you may have tried several ways, in vain, to fix the issue.

The good news is that you’ve come to the right place where you’ll learn all the possible causes of your engine stalling at idle when warm and how to fix each one of them. We’ll also reveal to you how much you can expect to part with in each case. 

So, why does the engine stall at idle when warm?

Many things can cause your car’s engine to idle lovely at the beginning only to disappointingly stall after warming up. These include but are not limited to the following;

  • An overheating engine control unit/engine control module (ECU)/(ECM) or ignition coil.
  • A dirty or bad idle air control valve.
  • Compression loss.
  • A bad crank position sensor.

Causes Of A Stalling Engine When Warm

1. An Overheating Engine Control Unit/Engine Control Module (ECU)/(ECM) or Ignition Coil

It’s basic scientific knowledge that heat causes expansion. If your car’s engine has an overheating problem, the engine control unit (ECU)/engine control module (ECM) and the ignition coil are some crucial components that can be adversely affected, becoming too hot and expanding unexpectedly. 

This expansion can break or separate the internal circuit within the ignition coil, causing it not to be able to conduct the electric signal to the engine control unit or engine control module.

Consequently, the ECU or ECM will not be able to naturally signal the sensor to trigger the spark plugs. As such, the engine will starve for power and eventually stall. 


Fix whatever is causing your engine to overheat such that the essential components such as the ECU/ECM and the ignition control coil aren’t incapacitated by too much heat.

Nonetheless, a lot of issues can cause an overheating problem for your engine. These include a damaged radiator, low or contaminated coolant, and loose, clogged, cracked, or damaged hoses. 

2. A Dirty or Bad Idle Air Control Valve

Your engine motor is what keeps your engine running, which means if it stops working, the engine also stops running–it stalls. Usually, it’s the enrichment injector that keeps the motor running at cold temperatures.

But the air control valve immediately takes over from the injector after the motor has warmed up. If dirty or faulty, the ACV may not be able to perform this function effectively(keeping the engine motor running while the engine is idle), causing the engine to stall. 


If your idle air control valve is dirty, try cleaning it to see if the engine stalling problem goes away. If this doesn’t fix the problem, it could be possible that you have a faulty ACV. In that case, try replacing the control valve with a new one to see if the problem goes away. 

3. Compression Loss

After too much wear and tear due to neglected oil changes, bad combustion over time, and other issues, your piston rings and cylinders will loosen up to a bad extent, causing compression loss.

That means they’ll have trouble mating as well as sealing properly when the engine heats up and the cylinders expand. 

Consequently, the combustion gases will begin to blow by the ring-cylinder surfaces, causing each stroke to lose power. As such, each stroke will not be powerful enough to maintain engine rotation when the engine is idle at warm temperatures. Eventually, the engine will stop rotating and stall. 

On the contrary, the ring-cylinder surfaces will remain tight against each other while the engine is cold. In this case, the combustion gasses avoid blowing by and the engine will be able to run without stalling. 

To determine if it is compression loss caused by loose piston rings and cylinders, perform a compression test with a compression tester.

Test each cylinder’s compression, noting down the results. Generally, the bare minimum compression for engines is 90 psi, even though it may be higher or lower for your engine, depending on your car model. 


Have your cylinders re-honed and invest in new piston rings. Or just replace your engine altogether, which would be much easier even though you’ll pay more. 

4. A Bad Crank Position Sensor

Oftentimes, a bad crank position sensor is the culprit for the stalling problem after the engine has warmed up while idling. Once the sensor heats up, it stops working intermittently due to a fault. You’ll have to let the engine cool off before the sensor can begin to work again. 

Unfortunately, many car owners and mechanics often misdiagnose this problem as ignition problems simply because there’s normally no spark ignition. That’s because when the sensor fails, the powertrain control module(PCM) can’t time spark ignition.


If a faulty crank position sensor or electrical connector is the problem, replace the sensor or connector and the problem will go away. If it’s poor wiring, on the other hand, have the wiring around your crank position sensor and its connectors corrected by your mechanic. 

How Much Does It Cost to Fix A Stalling Engine When Warm?

Again, the answer depends on what’s causing the problem. For example, if it’s an overheating engine control unit/engine control module(ECU)/(ECM) or ignition coil, you’ll need to fix the root course of this problem. 

A lot of issues can cause the overheating problem for your engine, including a damaged radiator, low or contaminated coolant, and loose, clogged, cracked, or damaged hoses. 

For example, on average, fixing a broken radiator will cost $90 while replacing it will set you back over $300-$900, depending on your car make and model.

Similarly, topping back up or replacing your coolant will cost you between $100 and $200, depending on your car’s make and model. 


Having an engine that idles lovely at the beginning only to stall after heating up can be a frustrating matter, especially if you can’t seem to fix it.

A lot of issues can cause your engine to behave this way, including an overheating engine control unit/engine control module(ECU)/(ECM) or ignition coil.

Other culprits are a dirty or bad idle air control valve, compression loss due to excessive wear and tear of the piston rings and cylinders, as well as a bad crank position sensor.

The good news is that there’s an effective solution for each one of them as explained in this article.

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