What is the reason for the throttle not responding when the car is warm but working fine when cold?
4 Answers
Car throttle not responding when warm but working when cold is caused by a fault in the electronic throttle system. Below is relevant information about the electronic throttle: Working principle: The electronic throttle is essentially an electronic throttle body. When the accelerator pedal is pressed, it does not directly control fuel injection but rather regulates the throttle opening. Throttle cleaning: If excessive carbon deposits accumulate on the throttle, it can affect the engine's normal operation. When cleaning throttle carbon deposits, the throttle needs to be removed. After cleaning and reinstalling, the ECU needs to be recalibrated; otherwise, the engine may experience increased fuel consumption in the short term.
I remember encountering a similar issue with my car before. When starting the engine cold, the throttle response was quick and acceleration was smooth. But after driving for a while and the engine warmed up, pressing the gas pedal felt like stepping on cotton – weak and sluggish acceleration. This is most likely a fuel system malfunction, such as a clogged fuel filter or insufficient fuel supply from the fuel pump at high temperatures. The fuel pump's efficiency drops when it gets hot, failing to meet the power demand. It could also be an issue with the ignition system, where spark plugs or ignition coils expand and deform when hot, causing increased gaps that affect ignition. The air flow meter in the intake system might also become less sensitive when heated, misjudging the air intake and causing fuel delivery issues in the engine. Later, I checked the fuel pressure and cleaned the fuel injectors, which alleviated the problem. I suggest you don’t take it lightly and go to a professional shop to check the electrical and fuel systems with a diagnostic tool. Otherwise, poor acceleration on the highway can be quite dangerous.
Over my years of repairing cars, I've seen many cases where the throttle won't respond properly when the engine is hot but works fine when cold. Common causes include a fuel pump overheating and reducing fuel delivery, or a partially clogged filter restricting fuel flow. Additionally, high engine temperatures can affect sensors - for instance, oxygen sensor measurement errors may cause the ECU to limit fuel injection to prevent engine damage. A severely dirty air filter restricting airflow is another possibility, as hot air is already thin and more prone to oxygen deficiency leading to power loss. Cooling system issues like a malfunctioning water pump or fan can also cause engine overheating that indirectly affects performance. I recommend starting with basic checks: test the engine's oil pressure and vacuum readings when hot to see if they're abnormally low. Then inspect ignition components like spark plugs for carbon buildup or erosion. Addressing these early can prevent major overhauls, saving both money and peace of mind.
I find it very troublesome when the car lacks power and the throttle is unresponsive during warm-up, especially in summer traffic jams where it might lead to loss of control. The core issue is often insufficient fuel supply or ignition failure worsening under high temperatures, such as an aging fuel pump expanding with heat, increasing gaps and reducing pumping efficiency, or oxidized wiring connectors causing short circuits that affect the electronic control unit at high temperatures. Poorly calibrated sensors, like the temperature sensor, can also cause the ECU to misjudge and limit throttle response. Additionally, engine lubricant thinning at high temperatures reduces protection, indirectly increasing friction and slowing acceleration. This is not just a performance issue but also a safety concern—failure to accelerate on slopes or during overtaking can easily lead to accidents. Stop and inspect the car immediately or send it for repairs; don’t wait until an accident happens. Regular maintenance, such as changing engine oil and filters, can help reduce such risks.
