Why Won't My Car Go Over 40 MPH?

February 15, 2024

When your car hesitates or can’t accelerate over 40 mph it’s a clear indication that something is wrong with the vehicle. The problem could be as simple as a stuck rubber mat under the gas pedal, or it could be a more serious issue such as a malfunctioning automatic transmission. Whatever the cause, it’s important to understand why your car won’t go over 40 mph so that you can take action to fix the problem before it becomes a serious road hazard.

One common reason your car won’t accelerate is due to a malfunctioning mass air flow sensor (MAF). This unit controls air intake and ensures that the correct mixture of air and fuel is injected into the engine. If the MAF sensor is dirty or not working properly, it can cause the car to stall and/or have intermittent delays when accelerating.

Another common cause of a lack of acceleration is a compression problem in the engine. Combustion engines rely on high compression to create the force needed to ignite and run the engine. When there is a compression problem, it can be caused by worn cylinder liners, cracked piston rings, or bad valves.

Another cause of poor acceleration is a problem with the throttle position sensor (TPS). The TPS is responsible for sending accurate information to the engine to control how much gas is used. If the TPS is not functioning correctly, it can cause the engine to run lean and hinder your ability to accelerate.


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