Mercury Grand Marquis Car jerks forward at high speeds Inspection at your home or office.

How it's done:

A mechanic will first check your vehicle by plugging in a code reader/scanner into the vehicle’s computer. The computer should be able to provide the mechanic with a better picture of what specific part or parts are failing.

If your vehicle has a bad or failing mass airflow sensor, the mechanic will begin by finding the sensor in the engine bay and checking for any signs of failure. The mechanic will check the wire harness connected to the sensor to ensure that all of wires are properly connected. After removing the sensor, the mechanic should be able to discover the nature of the failure and replace the sensor.

In order to check for a vacuum leak, the mechanic will examine the vehicle’s vacuum hoses and gasket. If he or she finds the source of the leak, the mechanic will replace the failed components and start the engine to make sure the leak has been fixed.

To check a bad fuel pump, a mechanic may have to remove the gas tank. Many modern cars have electric pumps located inside the gas tank. The mechanic will examine the fuel pump to see if it is the cause of the poor performance and jerking sensation. If it is the culprit, the mechanic will replace it and reinstall the gas tank, if necessary.

In all cases, your mechanic will make the necessary repairs and start the engine to ensure that it is now running properly. Once the repairs are completed, the mechanic can use the code reader/scanner to remove error codes and turn off the Check Engine light.