Cleaning a Catalytic Converter

Just get a cheap aftermarket replacement, it'll probably outlast the car...

I've had bad results from cheap aftermarket cats. Also, I need a CARB approved cat, so the cost is higher than regular cats.

I'd use testo ultra or keto burn to get rid of all the dirt. If you wait long enough, some prat will advertise them here.

I could, but the cost isn't too much lower than a good new cat. The state requires wrecking yards to test the cats before they sell them. I believe they need to re-certify them and most wrecking yards don't have the capability to do so. So they're typically scrapped for the platinum/palladium.

What about buying an entire wrecked lower mileage parts car. Swap the cat and then resell the parts car at a slightly higher price if possible ;-)

02 sensors!? The man is a big behind them.

Or so someone sez

Too much $$ to buy one. And the cat may also not be working.

Thanks for the recommendation.

I believe it is illegal for wreck and salvage yards to sell used catalytic converters to end user consumers.

Well that would bring the price down a lot.

Here in CA, they can sell used cats, but they have to certify them first. Junk yards don't have the time or the equipment to do this, so they're scrapped - good or bad.

Whoops, I stand corrected. In 2007. the state changed the law and a used cat cannot be installed, whether it's certified or not.

One thing to consider is your mechanic does not get any benefit when you put a bottle of whatever in your tank, so I am not surprised that a new cat is the 'answer'.

I have a 2002 Chevy Suburban with 263,000 miles with the original cat. Sometimes it will throw a P0420 code. It usually goes away on its own after a week or two. A long highway drive seems to clear it the fastest.

With a tank of a quality gasoline (top tier or whatever they're calling it) go out to the desert and find a stretch of road where you can run it good and hard for twenty minutes or so. Chances are you'll blow off whatever is built up on the cat.

Tell us how you do. (with nods to Van Halen's Unchained )

I was thinking the same thing. The mechanic that's working on it is not my regular mechanic. This guy owes me some money, so I have him doing work for me. He's a swap out type guy - not very good at doing real diagnosis. He works for the city, so they get away with that kind of stuff - where cost isn't important. In fact, I think the higher expenses he has, the more his boss thinks he does.

The Volvo is a turbo, so I'm not sure how good "blowing out" the cat will do. I'll give it a try and I'll throw a bottle of Pass or Don't Pay into the tank. In the past, I've had good luck with it.

I think it will still work with the turbo. You're just trying to get high exhaust volume through the cat when the cat is at a high temperature. I think it is key to have sustained operation like you would get climbing a long incline with your foot close to the floor. Some fuel system cleaner of whatever brand doesn't hurt either when doing this. They are usually any number of distillates that come off higher from the tower with perhaps some extra detergents added for good measure.

P.S. I'm not inclined to do any of those 'weird' cleaning regimens as I would be concerned doing more damage than good. An OEM cat for my 'Burb was $1,800 when I priced it out about six years ago when a undetected cracked exhaust manifold was pulling in excess O2 into the exhaust stream throwing 420 codes. Eventually I found the tiny crack in the manifold after replacing all four O2 sensors, etc. I'm glad I hadn't sprung for the cat because that would not have fixed it.

The motor pulls hard. The little 5 cylinder puts out 197 hp and 210 lb-ft or torque. The car has no problem going up hill at 100+ mph.

I'm not a fan of "cleaning" the cat, because I think it can do damage. Acids or strong bases can damage either the honeycomb or some metal parts. I was hoping someone here would know the chemical reactions to some of the cleaning methods to either warn me or to give me the green light. Putting lacquer thinner into the gas sounds like it could work, but I'm concerned it could eat up a part that is coated with enamel or it may damage the fuel lines.

Thanks again and I'll keep you posted.

With turbo and with the former recommendation, it will work pretty well. Turbos generally start working 1400-1800 RPM. So make sure you stay above 2000 RPM and stay some time (say 20 min) to heat up the engine and the exhaust system. If it is manual drive, you may prefer to stay in one gear lower to make sure turbo is on.

I used liquor on my merc @160K miles and it worked pretty well, too. There one should be careful about not keeping the liquor for too long in the fuel system. I do not believe it will damage the engine if one consumes the liquor in one shot (oh dont consider drinking it!). So keep the fuel in tank low and use the liquor preferably in a short time span. I got rid of my idle 700 RPM oscillations and the engine runs smoother.

Even at half the mileage, it is still the question of the devil you know, versus the devil you don't know. It's cheaper to keep her is my motto. Until it's not.

Yes, it's a beater. I was hoping to keep it for a few more years, but the smog test problem may prove to be the end of her.

I've owned lots of Volvo cars over the years. I drove a 1978 242DL to 340-350K miles. I don't know the exact mileage, because the odometer broke three times! It was still going strong when I gave the car to a friend of mine - I actually sold it for $500, but I consider it a gift, because it ran well, the paint was still good, the interior was good and it has relatively new tires. I saw him driving the car 5 years later - I lost track of him at that time, so who knows if it's still running.

This 2002 V70 Cross Country is still in good shape. Engine pulls strong. Tranny solid. Tires relatively new. Battery good, brakes good, exhaust good, shocks/struts good. It's the vehicle I use for my rentals. It's a wagon, so I can throw a lot of stuff in the back. In a pinch, it's a 5 passenger car. I can make a mess in the back and no worries, it's a work vehicle. Gets much better gas mileage than my GMC Sierra. And it's easier to drive. And it goes up hills better.

I just looked at a site where this guy drilled a small hole upstream of the cat and sprayed a can of carb cleaner into the exhaust with the engine running.

I'd say anything you do may, or may not, help.

But, for $3.00, why not give it a try.

What could possibly go wrong?

Ingredients in carb cleaner.

Scienceing.com

Boom !

I m thinking probably not enough O2 in the exhaust to go boom, but depending on hiw big the hole is and how recently it has run, maybe.

Of more concern to me would be coating the converter and then having the catylist and heat alter the carb cleaner into some lasting barrier.

Until we could get lyn to play the part of Mikey,we may never know.

Yeah. What could possibly go wrong spraying 8 ounces of tolulene into a closed red-hot glowing container. If God had meant us to have eyebrows, He never would have invented gasoline.

. . . or black powder.

I just took a look on Youtube and saw it. I may give it a try.

You mention cheap converters well I have used a few and they work great as a matter of fact when the local Ford factory had supply issues they used a bunch from my source and mentioned that they were superior to the factory units. Go with the low cost unit it will have a warranty should be just fine.

Thanks for the info. I appreciate it.

Thanks for the tip. ELM 327 chip - I'll look it up. Also thanks for the tip on TorquePro, Car Scanner and ForScan Lite. I have a couple OBD II readers that do a fair job, but I'd really like to get a professional scanner, but I don't want to shell out the $1K+ and the annual update fees.

Thanks again.

I believe all cars do this. The hot cycle burns the residue off, which includes not only sulfur, but other "stuff". When a motor burns oil, the honeycomb gets coated. If it's not too much residue, the cat will burn it off. If it's too much, the cat gets coated and doesn't work. Also, the residue can get baked on, forming a barrier for the exhaust gas to hit the catalyst.

I've also heard that the cat can be damaged if sensors cause the car to run so rich that unburned gas gets trapped in the cat and is burned there. Also, if the motor isn't sound (leaking valves, rings, etc) unburned gas can also get to the cat.

The other alternative therapy may be related to whether you drive like a pussy (or not). If so an Italian tuneup may help, i.e. thrash the living daylight out of it. Find a steep hill with a straight-ish road and give it heaps. Getting a nice glow going on in the catalyst could do the trick.

Another thing which may fool the oxygen sensor (and therefore the engine management system) is if you have an exhaust leak since the O2 sensor references the "outside" air and compares it to the exhaust stream. An exhaust leak can throw the reference O2 level right off.

I'm not the most gentle person when it comes to driving my cars. Though I don't beat them up (let the motor warm up before pushing it, letting the turbo cool before shutting down, etc), I do feel a car should be driven and I think it's actually good to push a car.

That being said, I don't think the cat is clogged up on the Volvo. I think it could be a weak O2 sensor or the car hasn't been driven "right" to get the monitor to clear.

Well, the O2 sensor is another failure mode.

Over time they get clogged with deposits and the pumping speed drops, shown as an increased cycle time. This should give a fault code, but a new O2 sensor would be a cheaper first step than a catalyst replacement.

My Grandfather taught me many things. One of his best was the simple fact that you can get a dead horse to move.

If you have a big enough stick and swing it hard enough the horse will move.

It's still dead, but it moved.

I can sell you a stick my friend.

If I had confidence in the mechanic, I'd just buy the cat. I don't want to waste money and since the CEL isn't on, I'm thinking that the cat is okay. I've heard that the catalyst monitor can be tough to clear - odd drive cycle required to clear.

My back up plan is to try to clean the cat.

I hear that VW has some old emissions chips they need to get rid of.....

Then I could get 50mpg on the old Volvo!

Maybe this :

Cataclean liquid catalytic cleaner

Walmart

Cataclean.com

$23.96

Thanks for the tip. I heard this is the stuff to use to clean the cat.

One consideration I haven't seen mentioned is that metal containing compounds can deposit metal on the catalyst and passivate the reactive surface. In the good (bad or indifferent) old days, a tank of leaded gas would contaminate the catalyst with lead and effectively eliminate the reactive surface. With metal contamination, there is no effective method to reactivate the catalyst surface.

Just out of curiosity, how is the effectiveness of the catalyst sensed by the monitoring system? Could you put two marginally bad converters in series to make an effective good one?

Here in CA, the smog shops do a visual inspection of the vehicle. Though I haven't seen them look at the cat, I do know that they open the hood. Putting a second cat in line may work, but that's quite a bit of modification and the added back pressure isn't something I'd like to have.

The driving cycle to clear the catalyst monitor is precise.

Engine below 95 deg F

No CEL

Turn ignition to on for 5 sec (don't start the car)

Turn the AC off

Start engine

Idle 10-20 seconds

Accelerate to 43-50 mph gently

Drive at a steady throttle 43-50 mph for 15 mins - CC off

Engine brake to 18 mph - release gas pedal

Stop car. Leave engine running

Idle for 1 minute

Accelerate to 43-50 mph gently

Turn AC on

Drive 43-50 mph for 5 minutes

Stop car. With engine on, check monitor to see if it cleared. If not, turn engine off, cool down to 95 deg F and repeat cycle.

I imagine you have experience with the inspection in CA and they are probably one of the most strict. I have gotten the dreaded P420 code on my 05 toyota and also wondered if it was possible to clean a cat. I have one of the little bluetooth obdII readers and torque lite (the free version). A few years ago of course the code came on right before I was due for inspection. When it happened I reset the code and drove it well over 100 miles and followed the drive sequence like you stated for passing the tests but to no avail. I asked a guy at the inspection station if he knew what I needed to do to get the test to pass. He told me that I can pass inspection with up to two incomplete tests. I had only one (which was for the cat) and of course it isn't up to the inspection station since they can only plug it in and the computer tells them if it passes or not. I had them do the inspection and it passed without an issue so I guess he was right. This is my daily driver and I have never checked to see if the internal cat test ever completed after I got it inspected. Its been well over a year since I had the code and it has passed inspection since.

I found this right after I posted which states you can have one not yet read test in NY. I found something stating that in Cali you need all of them except for the evap one complete so I guess that doesn't help you.

In CA, if you have a 2000 or newer car, the only monitor that does not need to be cleared is the evap. Can't get away with a catalyst monitor incomplete anymore!

My 2000 MR2 had an evap code that drove me crazy. I don't have a smoke machine, so I went on line and with the symptoms my car had, I figured it was the fuel filler tube, gas cap, gas line tubing, evap tubing or the check valve (the one on the gas tank). When I parked on the hill with the car tipping toward the drivers side, the odor was stronger, so the first thing I tried was a new gas cap. No change, bummer! I watched a couple Youtube videos and I figured it was the check valve.

That meant I had to drop the gas tank and remove all the stuff on the shelf behind the seats. I was able to squeeze my hand above the gas tank with only slightly dropping the gas tank. Check valve cover out - good! Gas and vacuum lines removed - wow, that was tough! Check valve out - good. Seal out (and not dropped in the tank) - good. Condition of seal was okay, but the check valve was almost in two parts - that was my problem. New gasket lubed up and in place (and not dropped in tank) - good. New check valve installed - good. Hoses connected - good. Gas tank back in place - good. All the junk on the shelf put back in place - good. Car starts ... yes! No P0440 code! Yes. No smell of gas! This was a tough one!

They clean catalytic converter elements on industrial engines all the time. Not sure how it's done, but we used to sell them and would routinely send the old ones out to be cleaned. Of course, they are made with removable elements and your vehicle wasn't.

Why don't you have someone actually measure the emissions and determine if the problem is with the converter or the sensor?

My mechanic should do this, but he believes in swapping parts until it's fixed. That's why he wants to change the cat. There is no P0420 code and the only problem I have is that the catalyst monitor won't clear. It could be that he's not doing the correct drive cycle or it could be a lazy O2 sensor or a bad cat.

I think I'm going to pull the car from him and put my scan tool on and see what the voltage at the rear O2 sensor looks like. A smooth output = good cat and good O2 sensor. I saw a video where they pumped a good stream of propane into the intake and watched the O2 sensor output. If it wavers, the cat is weak. If it wavers, but there is a delay when the propane is turned off, that means the cat is storing O2, which is a good sign.

I'm going to be busy this weekend, so maybe next weekend I'll do it.

I don't know the pros & cons of cleaning the cat but know that those codes can be down to O2 sensor. On my own vehicle you can buy a little extender that takes the O2 sensor out of the direct gas flow to reduce deposit build up. Might be worth cleaning the O2 sensors first. I also use TorquePro, great tool for keeping a check.

I've been told about putting spacers between the O2 sensor and the pipe. I need to test the O2 sensor (rear) to see how it's operating and to check on the cat. My mechanic doesn't know how to do it, so I'm going to pull the car from him.

I also need to pick up a better scan tool. I've received some good recommendations here!

Thanks for your input!

I see your heading in the right direction by hooking up your own scan tool. I plug mine in if any of my cars hiccup.

Here's some quick thoughts:

Your's is a 2002 Volvo. That means that your cloned reader may work well enough to get you a good start finding out what's actually wrong. I first started by using TorquePro after I bought my clone. You might as well spend the $5 and get the full version because the information you get from it is much better and there's more of it.

Make sure your engine is at operating temperature FIRST.

Don't start by reading the O2 sensors. Start on the TorquePro by hitting the Test Results button and letting that run. That's where I found that my COP's on cyl 2, 3 and 5 were the ones with high amounts of misfires. Anything that comes up in red with an X is what to look into first.

When you have that information, hit the fault codes button and see what kind of DTC's you have. Make sure you at least take screenshots of all that information for future reference. You can then clear all the DTC's.

This will give you a clean PCM (Power Control Module). I don't know if you know how to navigate TorquePro, it's not hard if you don't. You want to set up a profile for the Volvo to make it easier to save readings. TorquePro will also tell you exactly what sensors are available for reading which will come in handy for setting up the Realtime Information.

It's easier to find out what the trouble points are, set up the Realtime Info with the things you want to focus on, and start with a clean PCM. The stored DTC's and faults could have been sitting in the computer for a really long time and are of no value for the present problem and may only serve to confuse.

Another side point: When I bought my Real Elm reader, it took exactly 2 weeks from when I ordered it on a Monday until the Friday after next when it arrived. You don't have to re-buy the TorquePro app when you get the real Elm, your good there. With the Volvo, the Car Scanner app is more hard hitting, but "prefers" a real Elm (not a clone) so I wouldn't worry about it until you get the real Elm.

ForScan flat out tells you to download their DEMO app and see if your reader will be identified by the app. The BAFX reader I got from Amazon only got so far as the ForScan telling me that "No ELM Present'. That ended that and I started looking for a real elm that I, like yourself, would not have to buy a $500 (and always up) software package. The rest is history, I am delighted with the V2.2 WiFi I bought. It's always been right and all the live readings are accurate.

OBDII is the only practical way of troubleshooting any car. You should find some time to find out how it works. You don't need much if your like me, just trying to keep them running without a huge expense. It sure makes the "Check Engine" light not so much of a worry anymore.

I always wondered what the guys at the well known tire store starting with an F were going to do when, after charging my daughter (ME), $3000 to change the front Cat and it NOT being the trouble. After all, they were absolutely positive they were right.

Great info!

My 2 scan tools are a Zurich and a Harbor Freight. The Zurich is a cheap portable one that I throw in my bag. The HF is larger and it's quite a bit better and gives me more info. It also does a better job when clearing codes.

I haven't bought one of those bluetooth ones yet, though I like what you and others here have written about them.

thank you for this information!

Volvo V70 XC update:

My mechanic got the catalyst monitor to clear. Here's how he did it. The catalyst monitor won't clear if the CEL is on. My car has an slight leak in the closed fuel system, so it fails the evap test and throws a CEL. I told my mechanic to fill the tank, clear the CEL and drive the catalyst drive cycle. Lo and behold, the catalyst monitor cleared and my car passed the smog check!

New things I've found about my V70.

1. The car is strong and drives well. Turbo is still working and the car pulls hard!

2. My rear brake lights and turn signal light went out. I replaced the bulbs and everything was perfect. Then, after a long drive in the rain, the lights were out again. The turn signal bulb was good, but for some reason the dash warning message says bad turn signal bulb. Since it works fine, I'm ignoring the message. The brake lights are a different story. Bulbs are good, yet they don't light. The CHMSL does light up. Hmmmm! I traced the wires to see if there's a grounded or open line. All good. I had my helper push the brake pedal and I had no power on the circuit. I traced the line back to the rear fuse box and no power. I went to the Volvo forum and they said to look for the blue relay - it goes bad. Being the company they are, Volvo's fuse box is only partly visible with the inspection cover off. I had to pull the entire rear panel to get to the relay. No blue relay!! I started pulling relays and swapping for others in the box - nothing. There were two relays left and both didn't have a matching one to swap. I pulled the first one and took the cover off. I ran 12V to the pins and tested the switched side - works perfect. I pulled the second relay and I was about to remove the cover when I realized it was a double relay. I pulled one of the known good relays and put it in the top slot - no change. I moved it to the bottom and sure enough, the brake lights work. After doing some research, I found that there's a recall on the relay. Volvo's fix is to replace the double relay with two new relays (different from the existing ones). I haven't had the time to put everything back together, so it hasn't been to Volvo for the fix. Maybe tomorrow???

I also changed the license plate light bulbs, however when I pulled the socket out of the lens, it broke into pieces (the socket). I ordered a new part from the dealer - came the next day. I had to take the inner panel out to change the harness. Well engineered piece! One thing I found out is that the liftgate is made of a composite material. No rust and saves weight!

The more I drive and work on this car, the more it impresses me. I'm getting ready to head out to the taco place and I'm taking my Volvo!

ps - 2,000 + miles since it passed the smog test. And, I've let the fuel tank go to near E and no CEL. The evap problem mysteriously fixed itself! Looking for many more miles from my Volvo!

thanks! I have two cats at home and your article is just salvation for me. By the way, for cats it is very important to choose best cat food to prevent vomiting here to avoid any allergies and diseases that can lead to sediments for your cat.

Toxoplasma Gondii strikes again.