SeaFoam makes a product called "Deep Creep". This product is the easiest method of getting the stuff directly into your intake. Take the air tube off at the throttle body after you've run the engine long enough to get it up to normal operating temp. *this is the most important part so the seafoam can actually do the best job removing carbon buildup* after the engine is hot, remove the intake tube at the throttle body. DeepCreep allows you to spray it in any direction, even upside down, so spraying it into the intake is an easy proposition. Once you have the intake tube off the throttle body, start the engine and let it idle for a second or two. When it's idling at it's normal idle speed, use your hand to operate the throttle plate and begin spraying the seafoam directly into the throttle body. Use the throttle to keep the engine running while you are spraying. I use about 25%-30% of the can while the engine is running. It'll start stumbling and will probably try to stall, but I haven't been able to stop the engine with this stuff, so it's best to have an assistant to turn the key off for you. Once you've got about 1/4 of the can sprayed through the engine, have your assistant turn off the key while your still spraying. This will ensure un-burnt seafoam is allowed into the combustion chamber as the engine stops. After the engine stops, open the throttle plate all the way and continue to spray for a few more seconds paying special attention to hit any carbon deposits that build up around the throttle plates sealing surfaces in the throttle body bore. If the deposits are very heavy on the backside of the throttle plate or on the throttle body's bore, you may want to use a shop towel or tooth brush to free up the hard deposits. I too agree that the 5min suggested time is WAY too short for this stuff to do a really good job. I usually let it sit for 15-30 mins at least. Once your pretty sure you got all the carbon you can see removed from the throttle plate and the throttle body, take a break and have a beer or a coke while the seafoam works it's chemical magic. Once you've waited for the stuff to penetrate, reconnect your air tube and fire it up. I usually hold the throttle at WOT until it clears at least 2 of the cylinders and can run on it's own (try not to rev it above 3 grand for the first few minutes as the seafoam has effectively "washed" the cylinder walls and will allow considerable oil blow-by until the rings have had a chance to clear themselves of the leftovers). Once the engine is idling fine on all 4 (you should notice a smoother idle than before the procedure) the vehicle should be driven for at least a mile so the remainder of the seafoam can be sucked out of the crevices of the intake manifold. I prefer to drive it "spiritedly" for the first mile or 2 making a note to use the engine to decelerate the vehicle from a moderate rpm. (about 3.5g or so) a few times to help 'exercise' the rings. This, in conjunction with a few full throttle takeoffs, effectively expand and contract the piston rings against the cylinder walls (just like breaking a new engine in). The reason for this is it gives the seafoam a chance to work it's way into the rings and break up any sludge that might be causing sticky rings and oil blow-by before the seafoam is all burned out. This stuff is indeed O2 sensor safe from what I can tell. I've done a pre and post inspection of my O2 senor on an older car I had when I used to do this procedure at the Chevrolet garage I worked at. The O2 sensor was Noticeably cleaner and healthier 'looking' than before the run, verifying that seafoam's cleaning effect does indeed continue beyond the combustion chamber. I've also never had a problem with converter's running this stuff. As a matter of fact, I was able to 'save' a converter after a car blew a hole in a piston and sent a lot of oil through the exhaust system. After a few treatments, the foul odor coming from the tail pipe was gone and there didn't seem to be any lack of performance after a new engine was installed. This is nice stuff indeed!
I also run one full can in the fuel tank at every oil change and at least once in between oil changes.
As far as running it in the crankcase before an oil change, I can't comment on that. I'm sure the best time to do it would be once the engine is up to temp., and then it should only be run for 15-30 mins., and the car shouldn't be driven anywhere while it's in. I personally use AmsOil motor flush for this purpose, and before that I used Marvel Mystery Oil, also a good product for this purpose.
I just performed the intake procedure on my jeep yesterday, then took it for a spin on the highway. The idle is smoother again and pickup is restored back to normal. My jeep runs a little on the rich side still, so doing this once a month or so is a must to keep it from fouling up too much.
