Car Won’t Accelerate Past 40, No Check Engine Light

Causes

There are a few possible causes for this problem:

Fuel delivery issue: This could be caused by a clogged fuel filter, a faulty fuel pump, or a problem with the fuel injectors.
Airflow restriction: This could be caused by a dirty air filter, a blocked throttle body, or a problem with the intake manifold.
Ignition system issue: This could be caused by a faulty spark plug, a bad ignition coil, or a problem with the ignition control module.
Transmission issue: This could be caused by a slipping transmission, a faulty torque converter, or a problem with the transmission control module.

Troubleshooting

To troubleshoot this problem, you will need to perform a few tests.

Check the fuel pressure. This can be done using a fuel pressure gauge. The fuel pressure should be within the specifications for your vehicle.
Check the airflow. This can be done using an air flow meter. The airflow should be within the specifications for your vehicle.
Check the ignition system. This can be done using a spark plug tester. The spark plugs should be firing properly.
Check the transmission. This can be done by having a mechanic drive the vehicle and observe the transmission’s operation.

Repair

Once you have identified the cause of the problem, you can begin to repair it.

Fuel delivery issue: If the fuel filter is clogged, replace it. If the fuel pump is faulty, replace it. If the fuel injectors are clogged, clean them or replace them.
Airflow restriction: If the air filter is dirty, replace it. If the throttle body is blocked, clean it. If the intake manifold is blocked, clean it or replace it.
Ignition system issue: If the spark plugs are faulty, replace them. If the ignition coil is bad, replace it. If the ignition control module is faulty, replace it.
Transmission issue: If the transmission is slipping, have it rebuilt or replaced. If the torque converter is faulty, replace it. If the transmission control module is faulty, replace it.

Conclusion

If your car won’t accelerate past 40 and there is no check engine light, it is important to troubleshoot the problem and repair it as soon as possible. This problem can be caused by a number of different issues, so it is important to have it diagnosed by a qualified mechanic.