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Fix to the CAT to get SMOG passed?

1999 Acura Integra Auto 144k

NO is the only problem - other measurements are much lower than the MAX values.
2021 Results compared with others:
Test MAX AVE 21-MEAS 19-Retest 2019 2017 2015 2013 2011
15mph 467 67 357 146 693 462 445 442 246
25mph 754 62 1079 646 8 34 44 78 72

2019 Re-tesst increased the NO value at 25mph from 8 to 646! Historical max for NO at 25mph is only 78!
Mystery is how it jumped from 78 (or 8) to 646 after all the tune ups?
Before re-test, I used CatClean as well.
Did CatClean brought the carbon into the CAT and resulted in high NO at 25mph?

Scotty Kilmer:
He says he poured 1 gal of Shop solvent into the half tank of gas and drove - he fixed 100’s of cars.
Other think he said was remove the CAT and soak it in soap overnight.

OTH, NO is worsened at 15mph up until I used CatClean. Last test, it is only 100 lower than the MAX value. Until the 2019 failed SMOG, I do not warm up the car for SMOG as it had reliably passed. High NO at 15mph may reinforces the idea of aged CAT. Yet it might be cleaned?

There are others using CRC and Heet to pass the SMOG.

Any recommendation looking at the SMOG measurements?

Also, I use Long Life coolant (5 yr) - I still change every 4 yrs. Last time I did it was in Summer 2017. I am driving 4k annually on this car. So my Air filter is 2yrs old with 8k miles. FI cleaner (red bottle) was used in 2019 as well. Mobil1 oil was put in 4k miles ago. Battery and Alternator were checked to be fine. O2 sensor is a few yrs old from Honda.

A catalytic converter cannot be cleaned. No magic in a bottle will make a major improvement. About the only thing you can do is make sure to have a new clean air filter then take the car for a 30 minute ride on the interstate to get the cat hot with the engine running efficiently. That will burn off any unburned material on the cat surface. With the age of the car I think your cat has reached the end of it’s useful life.

How old are the spark plugs?


To me the solution is simple: get a new catalytic converter.


Just how many tune ups did you do in 2 years ?

That might well be - my first gen Integra failed and on re-test it passed. But 2 yrs later it failed miserably.

This one hasn’t reached there - so wondering if I am missing something!

@Tester’s post inspired me to think twice. So I posted the data.

Scotty Kilmer and a Reviewer on Amz also cleaned the CAT and passed emissions. This car might be a candidate! The after market CAT’s are guaranteed for 50k miles only.

In 2 yrs, I drove 8k.
I cleaned manifold, Idle Valve Control, changed oil, inspected air filter (8k mileage).

Spark is within the life (I have a record of it). Coolant & engine oil are not due for change. I changed the rotor assembly (name? - that connects the spark wires) at 100k with OEM.

What do u guys really do for Tune-Ups on a fuel injection car?

The car needs a new catalytic converter.

The engine in your car doesn’t have an EGR valve.

Instead, it uses a three-way catalytic converter to reduce NOx emissions.

And as the article notes, this is most common cause of high NOx on this type of system.


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Thanks @Tester

I don’t think this is true, however I agree that anything you add to the fuel isn’t going to help. Since a catalytic converter loses efficiency because the catalyst gets covered with soot and carbon, it stands to reason that if you can unbolt the cat, you can clean it with a solvent that dissolves soot and carbon. Assuming the honeycomb isn’t melted or broken into pieces, I would assume that one probably could clean a used cat with carburetor cleaner or brake cleaner, and that this might very well increase the efficiency enough to get through emissions testing.

A catalytic converter looses efficiency in 2 ways, one is the soot& carbon. Very easy to fix that, Get the platinum/palladium nice & hot for a few minutes and the junk burns off. The best way to do that is get on the interstate @ highway speeds for several minutes. That assumes the engine is operating normally, not burning oil, not dumping unburned fuel etc. The second way is the catalytic surface looses its ‘activity’ due to normal age use and exposure to things it is meant to convert, CO etc. Platinum and palladium are not catalyticly actively unless you pre treat it. A platinum (PT) necklace will not convert exhaust gases. The PT needs to be activated. A simple overview is to heat the PT to just under the temp it turns red and hold for a while. A delicate dance between hot enough but not too hot. Get it too hot and it is junk, not hot enough and it is inert. @TwinTurbo , anything to add here? He has experience with this also


They lose efficiency in 3 ways.

Coolant leak into combustion chambers


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This is the video from Scotty Kilmer:

I am considering using the Lacquer Thinner - the one at HomeDepot, is Klean-Strip brand - I am unsure about it. Scotty uses Shop brand - he says pure.

The Detail shop has UPC 699962084281 by Grow Automotive 1508 - it says 100% Virgin. This seems closer to what Scotty described - Grow automotive has several versions. His link to Amz for the Lacquer Thinner no longer works!

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You’re probably just going to need a new catalytic converter.

Scotty Kilmer is a hack who contradicts himself at least twice a week and resorts to clickbait titles and manipulation of Youtube’s algorithm to drive views to his inane videos that he craps out every few hours. His “descriptions” are meta-tags that don’t always have anything to do with what’s covered in the actual video, he also makes sure his videos hit the magic 10 minute mark by padding them out with " And here’s some bonus question and answers". It’s pathetic IMHO.


Well if the CAT were breaking down, then it will smell like “EGG” - I knew it from my Gen1 Integra. Right now it is not happening to my car.

People on that video tried it and reported its working. Only one guy stated otherwise.

Aftermarket parts only have 50k warranty!

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An egg smell from a cat is a potential sign of a failing CAT. All failing CATs do not smell like egg.

You can face reality and replace the CAT now or you can try to talk in circles until you have to replace it to pass. 22 years service life out of the CAT is noteworthy


This person ( sciconf ) makes all of his problems more complicated then they should be . And even thinking that Scotty Kilmer has a clue will not help.

Just have a certified shop put on a cat and be done with it.


Nah, too easy.


After a tune up went for another test as recommended by the mechanic - this time it failed on 15mph - tuneup caused NO to drop from 1079 to 639 at 25mph:
Test MAX AVE 21-Retest 21-MEAS
15mph 467 67 578 357
25mph 754 62 639 1079

I also realized that the O2 sensor was changed was the upstream one, for sure.
SMOG place suggested it could also be downstream O2 sensor.

Car runs perfect and no CEL either. Car was warmed up well.

When the AC issue (I mentioned in another thread) happened, the shop adjusted the throttle to give more gas - later it was reversed but might not have been to the correct level - I didn’t think it was a big deal since there is a slack on the metal cable - Is the engine still getting more gas at idle causing high NO at 15mph?

Lots of fascinating informative posts in this thread. Thanks to those posting info. This is very interesting to me.

Yeah. I’ve watched a few of his videos. Maybe it was just the specific ones I saw, but, well, he’s very entertaining but I wouldn’t let him within 50 feet of my car, much less trust him to tell me how to work on it.