A method for cleaning a combustion engine is disclosed wherein an apparatus with a cable is coupled to an on-board diagnostic port on the vehicle, and a service hose with a misting nozzle adapter is coupled to a first port on a vehicle. A controller monitors data from the on-board diagnostic port on a vehicle, where the data preferably includes the engine rpm, the catalytic convertor temperature, the engine coolant temperature, the MAF, and the MAP. The controller monitors information from the cleaning apparatus, and the information is processed to adjust the dispensing of the cleaning solution. The adjustment of the cleaning solution can vary the rate, volume, pressure, pulse interval, flow pattern, and duration of the solution in the engine.