Seafoam has Caused my P0420 Check Engine Light

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Howdy Folks,

I saw post another about Seafoam curing a problem, so I thought I'd post my experience where Seafoam caused a P0420 check.

I got an 04 Buick (less able) with only 40K miles on it, and I thought there might be some condensation build up in the tank over the years, so I dumped a can of Seafoam in just before filling up. Everything was fine until I got down to about 3/8 tank, then the MIL popped on while idling at a stoplight after about 30 minutes of driving. It was P0420, I cleared it and restarted the car and the light stayed off. Next trip though, again after about 30 minutes, MIL came back on while idling at a stoplight, another P0420. Then the factory original Delco battery began to fail, so when I swapped it out, that cleared the code again. By then I needed gas so I filled up, and the P0420 has yet to return, 2 tanks later.

The only thing I can think of is that there really was a lot of water in the tank for the Seafoam to soak up, and toward the end of the tank, I was pushing a lot of water through the combustion chamber and exhaust. Next time I fill up, I'm thinking about putting in another can, just to see if it happens again.
 
If your state uses booze in its gas adding something to absorb H2O is a mute point. E10 is used by states for supposed better environment.
Sounds more like a funky battery was screwing with you.
 
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Coincidence or the battery failure was more to blame than the SeaFoam.

As others have indicated, if you have ethanol in your fuel, any water was being passed through your fuel system already.

Leave sleeping dogs like and buy a beverage of your choice with what you would spend on a 2nd SeaFoam treatment.
 
Yes, we have ethanol, I never thought about its water absorbing qualities, one less thing to worry about. If it was the battery, I feel stupid for having the steppers in the instrument panel replaced. The wacky tachyometer might have been because of the battery too.
 
It wasn't the battery, as the light came back. I've only had the car a few months - the previous owner bought it when he was eighty-something, and only averaged 3K miles per year for 13 years. So the engine probably never saw anything over about 3000 rpm.

I went out and did about 3 0-60 runs where I was able get up to about 5500 rpm before it shifts, intending to blow out anything the Seafoam may have loosened. I cleared the code, and it hasn't come back, I guess time will tell.
 
It can sometimes take longer for the P0420/430 codes to pop up. It depends on when you meet the criteria for test to run. If the code comes back, just get a set of spark plug anti-foulers, screw the rear 02 into them and then screw the whole assembly into your pipe. Works all the time.
 
Originally Posted By: CT8
What is in Sea foam that does anything besides make smoke?


I really like the deep creep stuff myself. I use it every time I check or gap the sparkplugs on my vehicles. Spray it down the throttle bodies on the bike with the engine running and it cleans up the butterfly valves and significantly smooths out the idle which is VERY noticeable on a V twin. I also spray it down the carb and directly in each combustion chamber with the Buick. Same effect smoother idle with snappier response. I have used it with more modern vehicles and the effect is negligible though.

Works great as a gun cleaner/lube too
 
I doubt the snake oil did anything one way or the other. Pale oil, naphtha and a bit of IPA don't add up to a powerful cleaner. Spray creeper of whatever its called is the same thing in a spray can and equally worthless.
 
Originally Posted By: Trav
I doubt the snake oil did anything one way or the other. Pale oil, naphtha and a bit of IPA don't add up to a powerful cleaner. Spray creeper of whatever its called is the same thing in a spray can and equally worthless.


I use seafoam or water as a de-carbon methods. Both have similar results when used through a vacuum port in my experience. My pathy (stock) keeps its spark plugs a bit cleaner than the Buick (electronic ignition with beefier coil) and way cleaner than the falco (performance tune) manages. The pathfinder my ex gf and sisters Accords and my friends Altima did not respond to decarbonizing at all. I could not find a difference and neither could they. Modern vehicles with their constantly adjusting and optimizing ignition and fuel systems do not seem to build up the gunk that the older stuff does.

I do not know of anything positive from adding it to fuel but I definitely wouldn't call deep creep worthless. It does work very well as a gun cleaner and for keeping control cables clean and lubed. I would say its even better than dedicated cable lube.
 
Originally Posted By: Trav
If you say so, it must be another one of those products with unicorn tears that doesn't show up on a MSDS.


Plain old water doesn't show up on an MSDS but has been known as a pretty effective method for a very long time.
Deep creep is not the same as the regular sea foam. Pour some of each into a cup and leave it alone over night and see what happens. Deep creep has a lot of oil in it and does not evaporate away like standard seafoam does which is why it works as a pretty good lubricant for things like throttle cables and linkages.

I do not know if standard seafoam added to your fuel tank does anything. The stuff isnt magic lol
 
P0420 : Catalyst System Efficiency Below Threshold

Maybe you should start with figuring out what is causing that code. I doubt it is the seafoam. I think it is more coincidence.
 
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