Each time I wash my car I spray the cold engine with simple green solution. You can use any cleaner that is friendly to wiring and rubber. Then I start the engine and hose it off with low pressure water. Avoid the distributor but, anything else is fair game.

If your car starts to miss, you have found your vacume leak or misconnection.

Spray the water over the injectors and vacume hoses also. If you do this regularly, you won't ever need a steam cleaning.

by-the-way, steam cleaning is really not good for your engine or components.

Erling is "da man." Great looking engine bay!

I would definitely not use a power washer -- too much possibility of really making a mess. Just spray down your cold engine with something like 409 or the Castrol brand spray degreaser, and then hose it off with a low pressure garden hose. (you do not need to be ultra cautious with electricals, just do not go for the direct hit). You will be amazed at the effectiveness of that process. Like Erling, I then go over hoses and belts with appropiate dressings. A good trick is to mix Armor-all 50:50 with water and treat your hoses. Looks good w/o being too oily.

I have always had good results with solvents sprayed on a cold engine + surrounding areas, letting it work for ca. 10 min., then followed by steam cleaning. Afterwards the old elbow grease: Rags, brush and solvents.

To me, it's important not to stop there though. Now that I have a clean and eventually also dry engine bay, I have to assume that all rust protection and lubricating oil is gone. So I give all linkages etc. a treatment with the oil can, and wax all painted areas in sight, particularly around the body seams. The result also makes it a lot easier to keep the engine clean, I just hose everything down when doing the weekly wash. An easier alternative to wax is to go over the seams with a spray can of Tectyl (or similar) universal rust protection, but I like the glossy, like-new impression the car wax gives me. I also use plastic/rubber chemicals on the hoses and cables. Doing this once a year gives me an engine looking like this:

I second breadman's recommendation, however, if there is deep cleaning needed first, you may want to rent a power washer from a Home Depot, etc. Cover distributor cap with plastic bag to prevent/reduce water problems (as well as any other key electrical areas). Also use compressed air to assist in drying out any stray water.

"Simple Green" and a brush-don't wet any electrical components...
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Breadman '83 244GL 220K