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100 of 109 people found the following review helpful
on February 26, 2011
I have an 02 Chevy Tahoe with 127K on it. I've been throwing P0420 & P0430 codes for about 8000 miles, and lately they come back within a day of being cleared. Following the advice of another reviewer, here's what worked for me:

I used CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz. first to clean the MAF, let the car warm up for about 20 minutes, poured a bottle of Cataclean in the tank and drove for about 25 minutes (less than 1/4 tank of gas in the car). Then I cleared the error codes. Let the car sit while I was at work, drove it home, put a bottle of Lucas 10020 Upper Cylinder Lubrication & Injector Cleaner 5.25 oz. in the tank and filled up with Premium gas. I've driven for 70 miles and the code hasn't come back. I just passed inspection this morning.

I don't fool myself that this stuff will cover up a bad catalytic converter. But I can say that for me, whatever it did was good enough to allow the car's ECM to run the emissions test at least a couple of times without registering an error code. I don't care if the code comes back tomorrow. For the $35 that I spent for the three bottles, I have delayed a $2000 plus repair.
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79 of 88 people found the following review helpful
on May 17, 2014
As an ASE Certified tech myself, I never had any faith in anything that is dumped in the gas tank that claims it repairs catalytic converters (or anything else, for that matter). Understanding the fuel injection system as I do, as well as the ultra high combustion chamber temps and the incinerating heat of the converter itself, I knew nothing could survive such ungodly heat and molecular transformation to "clean out" the fuel system or the exhaust system, much less the catalytic converter itself!

But faced with a PO420 code myself and determining the problem was indeed my cat, I reasoned that a $25.00 investment was worth a shot.

I bought a bottle and dumped it in my tank at 1/4 full as the instructions say. I drove the 15 miles and then refueled. I reset my CEL and drove for over 100 miles with the light staying off. However, when I scanned it again, it still had a "pending" PO420 code even though light was off.

20 miles later, the light came on again so I was about to chalk Cataclean up as a big hoax. But upon reading more reviews, I found that some success stories stated that they acheived success only after buying a 2nd bottle and trying again. So I decided to give it a 2nd try.

This time I let the fuel tank go slightly below the suggested 1/4 tank and I poured the 2nd bottle in the tank. Instead of just a slow, normal 15-20 mile drive I went out on the Interstate and punched the throttle wide open to over 5k RPM for about a half mile. Then I slowed down and did it again, and yet again. All 3 times black exhaust streamed out the tail pipe. Then I just ran it steady at about 70 mph til the tank was almost empty.

I refueled with Sunoco 93 Octane because I thoiught it could only help the cause. I then reset the light, drove another 100 miles, and then did another scan. This time the "pending PO420" code was gone and the "codes" list was empty, stating "NO CODES".

I have driven over 1,000 miles since and still no light and no codes! So I can personally attest that Cataclean is an authentic winner! My advice to anyone is to drive it longer than 15-20 miles and don't be afraid to punch the throttle to "blow out" the carbon while the Cataclean is doing it's thing. It really did work for me doing it that way. Good luck to all!
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75 of 84 people found the following review helpful
on October 16, 2011
Another reviewer said this is not a miracle product, but for me it was. It truly has saved me $975. My 2000 Chevy Prizm check engine light has been off and mostly on, for like 10 months. It was time for inspection and I didn't pass because the light was on so I took it to a dealer (yes, I know, I know but the last time I didn't go to the dealer when the check engine light was on it went in the shop 5 times and was never fixed correctly until I took it to a dealer). On top of a whole host of other completely inflated and bogus repairs they suggested, they told me I had to REPLACE the catalytic converter to the tune of $1,000+. There was no other option. This was it. For an old, high mileage car it wasn't worth it and I came very close to just selling the car to a junkyard.

I have my own code reader Autel MaxiScan MS300 CAN OBD-II Scan Tool which I bought for $20. The dealer charged $60 to tell me the same code as this reader gave. The code was P0420 which is catalytic converter insufficiency.

I used the Cataclean exactly according to the directions on the bottle and right after pouring it in the gas tank, I reset my code reader. The check engine light came on 9 miles later. I thought maybe the Cataclean had not had time to work so I reset it again. It came on in 25 miles. I thought, it's getting better. I reset the code reader one last time, drove 50 miles with no problem, got my car reinspected and PASSED! I have now driven more than 100 miles and still no check engine light. I will recommend this product to everybody, all the time - and I mean all the time. Like you'll say, hmm, I wonder what I should have for lunch today, and I'll be like, hey did I tell you how great this Cataclean product is that I bought from Amazon? And you'll be like, yeah, about a 100 times.
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38 of 41 people found the following review helpful
on July 25, 2014
07/25/2014 - About two weeks ago my 2005 Honda Civic's computer threw a code and the engine light came on. I plugged in my ODBII reader to get the code(s) and got a P0420 Catalyst System Efficiency Below Threshold. Generally a mechanic will tell you that you need to replace the catalytic converter... about a $1,000+ job in a civic. I reset the computer and the engine light went out.

Given what the catalytic converter's job is, it stands to reason that it can get dirty and the screens clogged with carbon deposits. The same with the O2 sensors. Did some research on the web at found this product. The reviews were mostly good. In the meantime the engine light stayed off for a week. Once it came back on, I put a good fuel injector cleaner in it as I just had an oil change and I usually put fuel injector cleaner in at the same time. I reset the computer with my OBDII reader, and ordered Mr. Gasket Cataclean. Four days later the engine light came back on.

The cataclean product came and I waited and drove until I was below a 1/4 tank of gas so I'd run the max strength of the product through the fuel system. Put it in an drove mostly highway miles at 60 mph or better for 75-80 miles over two days. Last night on the way home from work the low gas light came on, so I pulled in to fill up and turned the car off. When I started the car after fill up the engine light went off on its own. So it looks like the product did the job.

Immediate results: Big difference in acceleration a whole lot more pep. Engine is quieter. Idle RPM's have dropped. The engine and fuel system have that little growl again like the car is breathing much better. I now assume that gas mileage will improve.

My car is not due for inspection for another year. If this product proves out over time. I'll put it in every 12,000 miles just for better performance and mileage. I'm at 122,875 on the odometer. I will update this review over the coming months as to whether the the engine light comes on again.

08-01-2014 - Engine light came back on with the catalytic converter code P0420, mileage 123,312. Car is still running better than before the treatment, and would have passed inspection. I will probably try another bottle in week or so and report back.
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10 of 10 people found the following review helpful
on September 22, 2013
I have been getting an intermittent P0420 OBD2 code and had the sulfer rotted egg smell typical of a catylitic converter on its way out. I have used other fuel system cleaners with no luck. I used one of these after hearing positive reviews from a friend who is an auto tech. Ran it for 40 miles and then filled the tank with premium and turned off the engine light using my scan tool. That was almost 600 miles ago and the P0420 code hasnt returned. (code used to come back every 30-40 miles) Plan to just use this stuff every few months instead of replace my cat. (saves about $1600) There is no magic cure for a bad cat and I'm sure it will be an issue again some day, but this got me through another year of emissions inspections without spending alot of money on repairs. I am very happy with the outcome.
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9 of 10 people found the following review helpful
on September 30, 2014
Ok, so I drive a beater. My daily driver is a 20 year old Cavalier with just under 100,000 miles on it. to be honest, I was pretty surprised to learn that I would even still need to have it tested at all. Surely, they have some type of exemption for antique/vintage cars? Or maybe just ones that are hopeless? I guess not.

Anyway, since I can't afford a new car right now, I needed to get my old one to pass. Having already given it a tune-up (new plugs, air filter, fuel filter, cleaned out the IAC valve, intake and MAF sensor), I was pretty confident that it would pass the first time.

I was wrong.

It failed for hydrocarbon emissions, exceeding the 0.80 limit with a reading of 0.88. Yep, she failed. Not by much, but still, some more work was needed. It was around this time that my mind began suggesting that maybe we should just buy a newer car. It was not long after, however, that my bank account reminded me that was not a possibility. so - back to the drawing board.

I remembered seeing a few products that promised to help vehicles pass state emission tests, sometimes even offering money-back guarantees, should you use their products and still fail. Cataclean (as far as I know) does not have any such guarantee, but - for the price I paid - it seemed worth the risk. I bought a bottle, drove my car until the tank was down to 1/4 full (as instructed), dumped the stuff in and drove it a good 50 miles to let it work its magic. Yes, I even revved the motor quite a bit, really opening the throttle up to increase speed and pressure, sort of blow-the-carbon-out strategy that I'd heard my father talk about a few times, back in the day.

I filled the tank up, drove a few more miles, then took it back to the emissions test facility for a follow-up visit. the friendly staff directed me (as before) to wait in the glass waiting area while they put my car through its paces on their dyno, measuring the engine's speed as they monitored the exhaust gases. I stood in the small room, staring helplessly through the glass, fingers crossed that my car would pass. Hoping that it would not blow up while trying.

A few minutes later, I was met at the far end of the waiting area by a man who smiled at me and held out a certificate of inspection, saying (somewhat incredulously), "Congratulations! Your car... passed.."

I looked at the new readings. HC emissions were reduced by a full 50% from the earlier test - down to just 0.44, well below the threshold needed to earn a clean rating from the state! The car felt better, too - the engine seemed to rev quicker, run a bit smoother. She felt more eager, and highway passing felt a bit easier. I might repeat the Cataclean treatment every 6 months, just to keep it running this well!

I can't guarantee that Cataclean will work for you. If, for example, you have a mechanical problem - broken/bent or burned valves, worn-out or completely clogged catalytic converter, serious misfire, etc - then NO liquid product is likely to help. But, if your car is in decent shape, and just needs a helping hand to get it through the test, I'd say that Cataclean is well worth a shot.
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17 of 21 people found the following review helpful
on September 25, 2014
Long story, short it worked!!! and passed the state inspection

Long story -- -Wife's car - 2006 Hyundai Sonata with a P0420 bank1 code.(check engine light) This is the catalytic converter and O2 sensor between the engine and the firewall (very tight and hard to get to) -The repair itself would have been over $400 bucks just for the parts - as the catalytic converter is connected to the exhaust manifold, and the O2 sensor is about another 100 bucks - - so that would be my expense and me doing the labor. If I took it to the dealer they wanted between 800 and 1000. So I had a decision to make.

I ordered three different products from Amazon. 1) Mr. Gasket Cataclean Fuel and Exhause cleaner. 2) CRC Mass air flow Sensor cleaner, and 3) Lucus fuel treatment - All three products came to 47 bucks- -

The job follows - - I disconnected the negative battery. By doing this, and leaving it disconnected for about 15 minutes, this cleared the check engine light. Next I cleaned the mass air flow sensor as directed on product label. this was pretty easy - just un-clipped the sensor wiring and sprayed the connectors. Next, I poured the Cataclean into the gas tank (note: open the gas filler cap before you disconnect the battery - as it has an electronic opener and will not work if the batter is disconnected) there was a bit less than 1/4 of a tank of fuel.

I told my wife to drive the car the required 50 miles (for a NC safety and emissions check they require the vehicle to be driven 50 miles after the check engine light has been cleared) -(actually told her to drive it like she stole it - hard and fast) then have the yearly exhaust and safety inspection done.

Prior to the inspection she needed fuel - so I told her to fill up with premium and add the Lucas fuel treatment to the tank.

Here's my guess on WHY this product (Mr. Gasket Cataclean) works - the P 0420 code is a inefficient catalytic converter - meaning that the catalytic converter is still working just not as efficient as government requires (they require 95% and above) - so it could have been working at 94% or less. Cataclean breaks down the carbon build up (somewhat of a solid) inside the catalytic converter and turns it into a gas which passes out the exhaust system.

If your catalytic converter is completely dead, or the O2 sensor is completely bad, none of these products will work - - but....... if everything is still working and just "dirty" then this process should help clean off the build up. Read your check engine light code - and break it down - understand the different "banks" (all V-6 and V-8 engines have two banks (1 and 2)) Bank 1 referrers to the sensor and converter associated with the # 1 firing piston, therefore bank 2 would be the other side of the engine
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5 of 5 people found the following review helpful
on April 22, 2013
I have a 2003 Toyota Camry with about 130,000 miles, and the check engine light had been going off for a while. My mechanic had reset it a few times, and he thought it was going off because of a leak in my exhaust system which was near the sensor for the catalytic converter. After he replaced the flex pipe which had the leak in it, the check engine light was still going off. He recommended I try this product before doing the $750 repair job that I would need to replace the catalytic converter. I followed the directions on the bottle, filled up with premium fuel, and in a few days the light went off on its own. Directions recommend using this product about 4 times a year, and after the success I had with it recently, I will definitely do that.
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7 of 8 people found the following review helpful
on October 30, 2014
I have a 2007 Nissan Armada. My vehicle has 135,000 miles and has four catalytic converters; one at each exhaust manifold, and one downstream from those. About a month ago, I had the dealer replace the driver side cats, at a price tag of over $2000 (non-OEM parts). My dealer told me that if the driver side had gone, the passenger-side converters were very close to going as well. Sure enough, one week thereafter the passenger side cats started to show signs they were plugged up. At no time did I get a check engine light and no catalytic converter code before the driver side cats plugged up, and the truck had to be towed to the dealer. So, I did not expect the check engine light when the right side converters started showing they were plugged up.

Long story short, my local Advance Auto Parts store had a buy one get one free sale of this product. I bought two and got two free. I ran two bottles when the fuel level in the tank was at one quarter to empty (about 8 gallons left in the tank) on two consecutive tanks tanks. The first time I drove the truck for 50 miles and on the second time I drove the truck for 20 miles, with the product in the tank. Two tanks after the last two bottles, and my fuel economy is at nearly 17 mpg (highway). Even prior to replacing the driver side cats, my fuel economy was at approximately 12.5 MPG, also highway. I think it goes without saying that this product does work. I wonder if the people for whom it hasn't, expected one bottle to fix their problem when it really should've taken two or three. Even if I had paid for each bottle, $100 is far cheaper than spending another $2,000 replace the passenger side cats, especially so close to Thanksgiving and Hanukkah.

I'll update this review in a month.
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16 of 20 people found the following review helpful
on February 21, 2011
Bought to clean out catalac convertor. It did work and was able to get by without having to replace catalac convertor to get a sticker. Would buy again and or recommend this to a friend.
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