Carburetor cleaner is the duct tape of spray solvents, a do-it-all can of mystery stuff that could strip anything but the soul from James Brown. But a couple of decades ago, the old standby got some company in the form of throttle body cleaner. A number of myths have grown up about the difference between them; the most egregious of which being that there isn't one.
The throttle body would seem, on the surface, to live a simpler life than the carburetor. A throttle body, by design anyway, is just a big air valve; it doesn't have to carry or meter fuel the way a carburetor does. But while the throttle body doesn't have to contend with the resin-like varnish that constant exposure to evaporating fuel causes, it does have to deal with something worse: vaporized and sometimes fully liquid oil, dust and dirt.
Gasoline contains a certain amount of solids or near solids, atoms or molecules that are too heavy to vaporize fully when exposed to heat or vacuum pressure. These components stick to the insides of the carburetor and fuel system lines, creating a layer of amber-colored varnish, like that on a hardwood floor. The oil that makes it through your car's positive crankcase ventilation valve, like varnish particles, sticks to the throttle body and idle air control passages. There, it soaks into and catches dust and dirt that makes it past the air filter; the end result is a hard, carbon- like amalgam of dirt, dust and cooked oil.
The first myth about throttle body and carb cleaners is that they're the same thing, repackaged to assuage the concerns of people who know their car doesn't have a carburetor, or to make more money. No; carb and throttle body cleaner almost always cost about the same. The second myth about them is that carb cleaners contain some sort of dissolved penetrating oil, which impregnates into the metal and hangs around to lubricate all the delicate parts inside the carb. Not only is this wrong, it's the complete opposite of the truth.
Carburetor cleaners are first and foremost designed to quickly dissolve varnish, wash it away and then evaporate without leaving anything behind. The varnish layer is typically thin, so the carb cleaner does its best work when it does it quickly. Throttle body cleaner is just as powerful as carb cleaner -- more powerful in most cases -- but works slower to break up those big carbon deposits. Throttle body cleaner is like the forest fire to carburetor cleaner's nuclear bomb; it lingers, destroying not by brute force but by slow dissolution. Most throttle body cleaners contain some sort of glycol or detergent, which sticks to the throttle body passages and helps to prevent future buildup.
You can use a carburetor cleaner to clean your throttle body, but doing so creates two slight problems. The first is that you'll have to use a lot more carb cleaner to get the job done. Carb cleaner can break up carbon just like it does varnish, but you'll have to make numerous passes to clean it all out -- and even then, you'll still wind up spending some time with a brush or pipe cleaner. The second problem is that the carb cleaner doesn't leave behind a layer of surfactant, so the throttle body will quickly get dirty again. Of course, you might also look into replacing the PCV valve, PCV filter and air filter to reduce junk intrusion into the throttle body, but that's your call. You can use throttle body cleaner to clean the carburetor's throttle blades, venturis and anything on the outside, and it'll do a nice job of cleaning and protecting everything. But the surfactant might not mix well with your fuel, so you're better of sticking to dedicated carb cleaner for full rebuilds.
