Hello, Use super purple cleaner don't dilute and use a green pressure washer nozzel. Reduce the pressure on the pressure washer to about 1500lbs and spray the ever living sh-- out of it. don't be afraid to get it wet. you may want to spray it down several times, get under the engine as well and remove the splash pan and clean that as well. Remove the grille and spray the cleaner on the condensor and radiator, clean the fins and make sure you spray at 90 gegrees to the fins, otherwise you run the risk of folding them over and reducing air flow. If when you start you have a slight miss, or a bad miss, you may have to take the black coil cover off and remove all the coils and spray compressed air to dry out the spark plug holes and coils. Don't try to run the engine hot with a miss and dry it that way. could cause more problems.
Good luck. I wash all my engine bays untill they are squeaky clean, then I use a comercial spray preservative over the entire engine. It is not a silicone. I can't remember the name of it, but most detailers no what you would be talking about. Once you spray on that it will eliminate any oxcidation of the now nice clean aluminum.