Seafoam has Cured my P0420 Check Engine Light

Status
Not open for further replies.
Joined
Jul 2, 2013
Messages
17
Location
Minnesota, USA
To put everything into perspective: Vehicle in question is a 1998 Buick LeSabre with 166k Mileage still using original Catalytic Converter.

I bought this LeSabre when it had 148k Mileage. It idled just a little rough right at the day I bought it.
I drove it till 160k when on came the Check Engine Light stating a Random Engine Misfire. We guessed the Plugs and Wires may still be original so we put in new Wires & Plugs. That did not fix the Misfire Code.
With my Uncle's Vehicle know how He eventually narrowed down the Misfire Problem to a Bad Ignition Module. We replaced the Ignition Module with a used one from a junk yard, that fixed the Misfire and eliminated the Check Engine Light.

A few days later on came the Check Engine Light, this time stating "P0420 OBD-II Trouble Code: Catalyst System Efficiency Below Threshold (Bank 1)"

So we figured then a Clogged/Bad Cat. Converter.

While searching online for New Cat. Converters I ran across a Fuel Additive called "CRC Guaranteed to Pass". I used the Guaranteed to Pass as directed on the Bottle. By the time the Fuel Tank was nearly empty nothing much had changed and the Check Engine Light was still on.

I then decided to try Seafoam Motor Treatment https://seafoamsales.com/sea-foam-motor-treatment/

I used the Seafoam pretty close to as directed on the Can (1 ounce (US) Seafoam per Gallon (US) of gasoline.
The 1st Tank of Gasoline I had right about 16 Gallons in the Tank along with the Seafoam. Began using the LeSabre as usual. I Deliver Pizza so my Mileage Tacks up pretty quickly.

Within in the first 100 miles I already noticed the Engine starting to Idle Better, plus the engine hesitations at stoplights becoming less severe. I went thru the rest of the Tank and the Engine kept slowly running better.

Tank Empty, figured I'd try it again. Put in a full can of Seafoam into the very next tank full, this time I filled it to 18 Gallons.
Again all thru this Tank Full with Seafoam the Engine slowly ran better and better.

2nd Seafoam Tank Empty, figured I'd try it again. Put in the 3rd Can and added Gas to about 16'ish Gallons in the Tank.

With the Tank about 3/4 of Full of the 3rd Consecutive Tank with Seafoam Added, the Check Engine Light suddenly Disappeared.

When this All began I really believed it would not work, but it did work. The Seafoam removed the P0420 Check Engine Light.

The Engine now Idles smoother then when I bought it.

The Engine still hesitates slightly when cold, runs fine when warm. The Check Engine has not yet returned.

One thing odd, when doing a pizza delivery last evening, a few hours after the Check Engine Light had disappeared, I left the Car running when handing the Pizza to the Customer, I then noticed that very obvious Catalytic Converter Smell coming from the Exhaust, Had never smelt that from this car before.

To be on the safe side I plan to run 1 maybe 2 more Tank Fulls with Seafoam in it.

If you get a P0420 Bank-1 Code this Seafoam is Definitely worth a Try.
 
It's difficult to say(remains to be seen) whether the Seafoam did the job or the fact that, Seafoam was the 2nd dosage of cleaner to your fuel tank. Maybe 2 doses of CRC Guaranteed to Pass, may have done the job as well, who knows?

Anyway, congratulations and I hope this keeps working for you however, you may indeed need some new parts such as an O2 sensor or Cat Conv in the future.
 
With the CRC Guaranteed to Pass the Engine never ran better at all threw out the entire Tank Full of it.
With the Seafoam, within the 1st 100 miles of using it the Engine already started to run better. each consecutive Tank with Seafoam the Engine noticeably ran better and better the entire process till the P0420 Check Engine Light disappeared.

The Engine already Idle's much better then it did when I bought it.

It still does hesitate a bit when cold, maybe another tank or 2 with Seafoam will cure that Hesitation. Or like you say something else could be wrong with it or a new Cat. will be needed in the future. For now though at least the Seafoam Disappeared the P0420 Light and the Engine runs noticeably better
 
I thought Seafoam works better when sprayed into the air intake with the engine at highish idle via the brake vacuum line if possible.

A CAT does not smell unless it's a furry type, although some fuel additives can. Might well be a small hole in the exhaust or emissions gear.

Most warning codes for the CAT or EGR include bad connections or associated sensors (Solenoid in the case of the EGR). O2 sensors in particular don't last forever.

It would be worth getting all the hidden fault codes read, as the check engine light covers too many systems.
 
Last edited:
A dirty MAF can cause a P0420 due to a lean condition. Its possible the Seafoam has richened up your fuel to "cure" your problem ..

I would try cleaning the MAF first then have an infrared heat gun placed before and after your cat to see whats going on with it for piece of mind.
 
It's always good to start with a well running motor before chasing other emissions gremlins. Naturally you want a clean spark and good injection for this to happen, but the ancillary stuff assumes a good running engine.

I suspect this car needs a good 100 MPH flogging as well.
 
Back in the late 70s/early 80s, Cats had a rotten egg/sulfur smell to them on occasion. At least that's what I was told caused that smell. Cat farts.
 
Originally Posted By: eljefino
It's always good to start with a well running motor before chasing other emissions gremlins. Naturally you want a clean spark and good injection for this to happen, but the ancillary stuff assumes a good running engine.

I suspect this car needs a good 100 MPH flogging as well.
YUP A buddy of mine removed the vacuum line to the fuel pressure regulato and drove for 20 miles to load the cat with a rich mixture then gave the car an Italian Tune up. Cleans the soot out of the ceramic honey comb. Triple digit speeds aren't necessary, heat and high RPM are. I hold the 528e in 2 and run it up to the RPM limiter Speed is only 70 mph
 
Cat converters still have that smell, usually when the engine is under high load and running rich. Is possible the OP's misfire was contaminating the cat and when it starting running better it the extra heat and less unburned fuel created a pretty good "burn off" of the cat.
 
"Don’t worry if you exceed these amounts: Sea Foam only contains petroleum-based cleaning and lubricating ingredients that CAN’T HARM your engine or fuel system components."

Is this additive feature unique to Seafoam?
 
Status
Not open for further replies.
Back
Top