DIRECTIONS:
GREAT ADVICE from MTL_4runner:
I put this in another thread but seems like it would be good to post it here too because there seems to be some issue when an engine hasn't been cleaned in some time and loose carbon can come off abruptly and foul sensors and spark plugs or clog catalytic converters. Here's what you want to do to prevent this....
You want to run the Seafoam fairly concentrated for the duration of the tank, so put at least 2 cans in (you can add as many as 4 on a full tank.....too many at once and you'll kill your gas milage for the tank so save the heavy doseage for later when you put it though the PCV hose), then fill the tank with the highest grade of gas you can get (ie 91+ octane or better, make sure it's a brand name like Chevron, Shell, etc) and run it until it is as close to empty as you feel comfortable (ie do your best to get somewhere between 1/8 tank and E without running out of gas). Try and resist the urge to top off the tank during that time even if the price of premium goes back down to $1 per gallon.
After your done the first part, then you can be pretty safe about running the next can straight in the engine (via the PCV or some other vacuum hose that goes directly into the intake). You can do 1/3 to 1/2 of a can each time for best results, but be patient after! Always remember to pour SLOWLY when your dumping it into the engine itself and then shut the engine off right after you finish adding the last drop. Leave it for at least 1 full hour and then restart and take it for a drive on the highway.
You may not notice a huge difference if your engine was pretty clean to begin with but I'd bet you'll see a decent improvement in gas mileage after with an engine that was in need. It is also suggested to clean the MAF when doing this for maximum effect (use the red extension tubes with the aerosol can to get the cleaner right down to the wires, but DO NOT TOUCH THEM.....after shake as much out as you can and air dry). I've switched over to using brake cleaner to clean the MAF because it does a much better job than electrical contact cleaner (with electrical cleaner the wires look better, but with brake cleaner they really look like new). Just be sure to let it thoroughly dry before starting the engine and pull the negative battery terminal to reset the ECU to relearn the new MAF readings.
For you guys in Canada, Seafoam is available at any NAPA store for just under $10 CDN per can.
PICS (courtesy of RunnerUp) of the PCV on a 3.4L 5VZ-FE Toyota Engine:
PCV with hose removed_____________________________________PCV hose removed, shown in relation to the throttlebody
Original post from 6/21/2004:
Over the last few months, my gas mileage has been dropping off horribly. Last monday when I filled up I got 13.8 around town (I've been getting 15 in town and 16.5 on the highway). That was the last straw - I had to do SOMETHING. I picked up a can of seafoam along with some TB cleaner and did a little late spring cleaning. I poured the seafoam into the PCV hose with the engine running like on the directions. On the first application, I poured it very slow (1/3 can), then shut off the engine (again, like the directions said). Five minutes later when I started it up, it blew more smoke than the batmobile. After all the smoke subsided, I gave it another treatment, but poured a little faster so that it was almost stalling out. (again, 1/3 can). After starting up, it BILLOWED smoke for several minutes, but the engine just PURRED after it was finished. It was the smoothest running toyota engine I've ever seen. While I was at it, I gave the MAF a good bath along with the air filter and the TB.
Well, that got me back up to 17.2 on the highway on our trip to the beach (still not satisfied).
While I was down there, I picked up another two cans of seafoam and put both into my tank at 1/2 full (4X stronger than in the directions). I ran this for about 20 miles or so, then filled up at a cheapie station ($1.69 when everywhere else was $1.86) and got back on the interstate to drive home. I filled back up here in Birmingham, and I ended up getting 18.1 on the ride home. Not too bad. I can't wait to see if it goes up even more with Shell in the tank...
Now on startup, instead of having to hold the key for a sec for the engine to fire, it starts right up with ZERO hesitation. The injectors and intake must have been pretty bad (106k and counting)...
If you do the seafoam treatment, I'd recommend SEVERAL cans so you can give the intake a good cleaning along with the injectors.