The vehicle speeds up and slows down with no change in the accelerator pedal position.
Perform the Diagnostic system check - engine controls.
The driver must be familiar with A/C compressor operation.
Make sure the Vehicle Speed parameter matches the value in the vehicle speedometer with a scan tool.
Ensure that the ground of the ECM is free of dirt and is fixed securely in the correct position.
Inspect whether the harness connector is properly connected.
Inspect the fuel type and quality.
Verify the Injector ID Code of each cylinder.
Check the scan tool data list.
Check for related Service Bulletins.
Observe the Fuel Rail Pressure (FRP) Sensor parameter on the scan tool. It is normal if the Fuel Rail Pressure (FRP) Sensor parameter shows 0.9 to 1.0 V when the ignition switch is turned ON without starting the engine after 30 seconds or more have passed since the stop of engine operation. If not, inspect for high resistance in each circuit and for any sensor failure.
Observe the Fuel Rail Pressure (FRP) parameter and Desired Fuel Rail Pressure (FRP) parameter while fully depressing the accelerator pedal with the vehicle in neutral and idling. The difference displayed should always be held to 5 MPa {725 psi} or less.
Observe the Accelerator Pedal Position (APP) parameter. It is normal if the Accelerator Pedal Position (APP) parameter changes linearly from 0 to 100% according to the accelerator pedal operation.
Inspect for air in the fuel system.
Inspect for water in the fuel.
Inspect whether the fuel is frozen.
Inspect whether the fuel filter warning light illuminates intermittently or frequently.
Inspect the fuel filter for clogging.
Inspect for fuel leakage from the pressure limiter and injector.
Inspect for collapsing, twisting, improper tightening, cracking, or clogging in the fuel system between the fuel tank and the fuel supply pump.
Inspect the vent valve and the hose of the fuel tank for clogging.
{The piping may be clogged due to foreign material from the fuel tank having entered the fuel system.}
Inspect the fuel supply pump operation.
{The fuel supply pump must be timed with the engine, and the adjusted value should be learned by the ECM.}
Perform the Cylinder Balance with a scan tool.
Perform the Injector Forced Drive with a scan tool.
Inspect the air cleaner, air intake duct, and intercooler for clogging, holes, or leakage.
Inspect for any condition that restricts flow within the turbocharger intake duct.
Inspect for a stuck intake throttle valve.
Inspect the inlet cover for clogging or air leakage.
Inspect the MAF sensor for dirt or damage.
Inspect the operation of the turbocharger control actuator.
Inspect whether the exhaust system flow is restricted.
Inspect the output voltage of the generator.
Inspect whether the EGR system is operating properly. (Euro2 and Euro4)
Perform the EGR control system check. (Euro2 and Euro4)
Inspect the relief valve and relief valve control solenoid valve for sticking. (Except Euro2 and Euro4)
Inspect the operation of the A/C.
Inspect the operation of the torque converter clutch. (Automatic transmission models)