Seafoamed the TC
Reply #34 –
Anything that isn't the correct mixture of HC's/NOx/CO/etc is "hard" on cats. Running rich is VERY destructive because the heat becomes overwhelming and the internals might melt/warp/plug....I'm no expert but there's a reason cat'ed cars say "Unleaded fuel ONLY". Leaded fuel will also destroy them. They are sensitive to contamination.
I don't see the point of running seafoam through any car. I'm sure it is a powerful solvent, but the only components you can't get to physically to clean by hand are the intake and exhaust valves. If there are no misfires from your exhaust, no "thwuh thwuhh thwuhh" puffing noises, then guess what? Valves are closing and holding compression. Same with intake, simply shouldn't hear backfiring (LOL)/puffing anything like that. If it were me, I'd rather take a garden hose tricking water, and spray that into the TB while holding 2-3K rpm. Just enough that it starts stumbling/slowing down. The old tale of throwing a glass of water down the intake won't work. The water will flash boil and knock loose carbon, but not with that small quantity. Cars that develop leaky headgaskets have super-clean combustion chambers where it leaks into, and over time, every day, washes things away. So that trick has to be done several times, I'd say 15-20 minutes at a time. And again, careful not to DUMP water in, don't want a hydrolocked piston...
And if you've got serious carbon holding valves open...you've got more important problems. A rough idle? Pull off the IAC/EGR/EGR plate and se all of the carbon out, clean everything with copious amonts of carb cleaner or something similar. Ideally have the upper and maybe lower intakes hot-tanked or pressure wash them out, off the car of course. But some seafoam isn't gonna remove all of the built up carbon + gasoline + oil vapor from the PCV that you see in the upper intake.
Finally, of course if you don't have to deal with a high-enhanced dyno-test emissions check, BLOCK THE EGR off, or unplug the vac line. This is all the main reason I have all of my cougars and my crown vic that way. EGR valve itself is going to start sticking, same with the IAC, potentially valves in the cylinder heads. Good ounce of prevention. I just question as to how effective Seafoam really is towards what you want it to do, especially after dealing with the long-ass smoke signal that would probably make the cops think you were roasting 'em LOL.