Cat codes, a tip and easy fix

[cclngthr]

If people are getting a P0420 or P0430 code, cat inefficiency code, one thing to look for in properly diagnosing it is where the long term fuel trims are at on each bank and o2 sensor voltage. Sensor 2 voltage should be within .100 of 1 volt at idle and at a steady rpm on a 1 volt scale. It can vary depending on the engine, but it should be above .650 volts at idle. Usually .800 is considered normal. LTFT should be below 5% on each bank at idle, the lower the better.


The main problem with both the Duratec and Ztec is carbon buildup. This causes false cat codes and makes it run lean. A regular cleanout is my recommendation.


Materials
WATER (plan on using at least 1 gallon, possibly more)
1 16 oz can of seafoam
1 squirt bottle, with a stream spray attachment.


I recommend slowly pouring water in the TB rather than the vacuum line. May have to do this fast enough with engine rpms at 3,000 rpm at hot engine temps. What you want to do is fog and steam up the engine everywhere. A vacuum line may not allow steam to get everywhere. After a while, try to pour enough water in the engine at a lower rpm to bog it down and let it die. Let sit for 20 minutes to let the steam cook in the engine. Restart engine (will be difficult to start) and rev up engine rapidly to shove crap out the exhaust. Should see a lot of gray smoke. Once smoke is pure white, let engine idle until running smooth.


Next, use the squirt bottle with seafoam in the TB and as you are spraying it in the TB, rapidly throttle the engine from idle to WOT fast enough not to overrev the engine, but to clear out the engine of carbon buildup. The rapid WOT throttle is to let seafoam into the EGR passages and through the valve itself. You should see black soot coming out of the tailpipe.


Did this with my contour which had these codes and everything is fine now. Will need to run the car on the highway a while to clear out the cats.

 

[squeek]

Drill coat hanger cats clear out even quicker.

 

[cclngthr]

Drill coat hanger cats clear out even quicker.

In areas where there is emission standards testing, gutting cats is not advised, nor allowed. It also does not solve the lean condition problem either. Solving the lean condition (under 25%, but above 10%) by decarbonizing the engine is generally advised.


Around my area, we do have emission inspections, which include visuals for emission equipment and function. Failure requires certified emission specialists to repair the vehicle up to $150 and if a waiver is granted, the cats guts have to be intact, and all emission equipment installed. If any part is missing, the cost of repairs will be over that $150 amount. A friend of mine owns a shop that is certified to repair emission equipment, and the state requires them to check the full function of the equipment and if a part is missing, they are required to deny the waiver. Using o2 spacers also can be spotted by the visual and this can fail the inspection as well.

 

[BrApple]

I would NOT recommend putting water into the engine.


It is a known fact that Contour PCMs have a tight tolerance for the pre-cat codes. And there was even an update to widen them. Because of this the pre-cat codes are normally false.


The easiest thing to do is to install mil-eliminators. This leaves everything functioning and pre-vents the pre-cat codes from setting.

 

[nmd003]

I've heard some old heads talk of cleaning using water, saying that it is better than using any chemical cleaner. I am skeptical though; I'd be afraid to hydro-lock my engine. I'll stick with seafoam or similar.

I've also had P0420 and P0430 caused by vacuum leaks. Fixed the leaks and the codes went away.

 

[cclngthr]

I would NOT recommend putting water into the engine.


It is a known fact that Contour PCMs have a tight tolerance for the pre-cat codes. And there was even an update to widen them. Because of this the pre-cat codes are normally false.


The easiest thing to do is to install mil-eliminators. This leaves everything functioning and pre-vents the pre-cat codes from setting.

The mil eliminators also alter fuel trims. You DON'T want to lean out these engines too much from stock. Anything above 5% on long term fuel trims is dangerous at cruise and idle. You want to keep that number as close to 0 as possible.


Water in an engine has been used for over 40 years to decarbonize an engine. Water chemically reacts to carbon by breaking that carbon down. It is a violent reaction, a .5 pound of carbon dropped in water will act line a huge fountain, water will shoot upwards to 50-60 feet in the air.


These engines are also known to carbon up easy; all Duratec designed engines are like this, including the similarly designed MZR Mazda engine. This is also known to Ford techline engineers. Dealer techs are instructed to check the long term fuel trims when customers complain of engine roughness and lack of power and lean codes as well as the cat codes. The instruction is to use a chemical to decarbonize the engine internals and cats or use water first then the chemical. Carbon gets into the LIM and UIM and rather than pulling the intake to physically clean out the internals and injectors, there is an option to use water and a decarbonizing chemical.


When I did this, I had pure black smoke thick enough to prohibit me from seeing anything over 3 feet behind the car for at least 5 minutes.


The cat is designed to require fuel trims under 5%. Anything over that will set the cat code. Cats also have a narrow optimal temp range which is between 700 and 900 degrees. Lean conditions raise that temperature to over 1200 very quickly. Too hot, the cat won't operate as designed; which is the same as too cold. You need fuel to cool the cat and keep it within that temp range.

 

[nmd003]

When I did this, I had pure black smoke thick enough to prohibit me from seeing anything over 3 feet behind the car for at least 5 minutes.

Any danger of clogging up your cats by doing this?

 

[cclngthr]

Any danger of clogging up your cats by doing this?

If it is done too fast, yes, but splitting it up between 2-3 different sessions avoids this.


On my car, I checked the state EPA history on the state emission tests and found the last passing test was in 05 (I have had the car a month) and each time, a P0420 code was logged. Several years the P0430 also was logged. 3 times the EGR P0401 code also was logged. One year a P0171 and P0174 lean condition was logged. I knew that the passages were blocked with carbon, and the engine and cat likely was filled with carbon.


On the diagnostics of both P0420 and P0430, one of the things techs are instructed to look at is carbon buildup. The LTFT readings also note that when they are above 5% carbon buildup can be suspected. A major cleanout usually solves the problem.


By water logging an engine, you are cooling the charge as well, and many performance shops install water injection as a way to gain power, as well as reduce the chances of carbon buildup.


I did my treatment several days apart in 2 sessions. One with plain water, and enough of it to smoke the engine with steam and clear out the intake. The second treatment was more water, and a heavier cloud of smoke. This broke down the carbon so the chemical would react with it more effectively and dissipate it easier. The extremely thick cloud of black smoke coming out of the exhaust cleaned the engine and cats enough to make both bank cats work and light up easier.


I let the car sit hot for about 20 minutes and drove it easier to let the chemical and water cook in the engine to allow the excess carbon buildup to be thrown out the exhaust. A lot of people would drive it hard, but doing it this way causes the engine to be cleaned more effectively and more thoroughly.


Car now has a better exhaust tone and the intake has a better sound to it at throttle.

 

[projectSHO89]

The mil eliminators also alter fuel trims.

Nonsense. The downstream sensors on a Contour have nothing to do with the mixture and cannot affect fuel trim.

The cat is designed to require fuel trims under 5%. Anything over that will set the cat code.

More nonsense. Fuel trims, in and of themselves, do NOT cause cat efficiency codes. LTFTs are generally allowed to go +/- 25%. STFTs can add another 10% or so to that range.

However, most valid cat codes, that is, those caused by dead or ineffective converters, are the result of some other problem that allowed excessive fuel to be dumped into the converters for too long. Misfires, vacuum leaks, bad O2 sensors, bad thermostat, and the like all cause the trims to be skewed rich and contribute to the eventual degradation or destruction of the converters.

As for the idea of using water to clean your cats, yeah, that's not a very good idea. The problem isn't carbon buildup in the converters.

Who are you going to believe, a guy who has owned a Contour for a month and just washed ashore here this month or a couple of guys who have been driving them and participating here for way over a decade.

 

[cclngthr]

Nonsense. The downstream sensors on a Contour have nothing to do with the mixture and cannot affect fuel trim.



More nonsense. Fuel trims, in and of themselves, do NOT cause cat efficiency codes. LTFTs are generally allowed to go +/- 25%. STFTs can add another 10% or so to that range.

However, most valid cat codes, that is, those caused by dead or ineffective converters, are the result of some other problem that allowed excessive fuel to be dumped into the converters for too long. Misfires, vacuum leaks, bad O2 sensors, bad thermostat, and the like all cause the trims to be skewed rich and contribute to the eventual degradation or destruction of the converters.

As for the idea of using water to clean your cats, yeah, that's not a very good idea. The problem isn't carbon buildup in the converters.

Who are you going to believe, a guy who has owned a Contour for a month and just washed ashore here this month or a couple of guys who have been driving them and participating here for way over a decade.

I have been working on cars a lot longer than you think. Try 30 years. Also have manufacturer specific training on servicing and repairing cars, Ford being one of the many mandatory trainings that I am required by my employer to have. I also have built, and fabricated engine components that don't exist. Try designing a set of heads for a V8 that are capable of using direct injection.


The rear o2 sensor parameters want the cat functional at a specific time frame. The PCM wants to get the cat up to a specific temperature within 20 seconds of startup. It uses the rear o2 sensor to accomplish this task. The PCM adds fuel to get it up to that temperature quickly, and monitors the status every 5-10 minutes by subtracting and adding fuel to see if the cat is doing what the PCM is programmed to do. The PCM in its monitoring of the cat will adapt the fuel trim, both long and short to keep the cat at the specific temperature and functional. If the cat is too cold, it will add fuel to heat it up. If the cat continues to run cooler, and does this for 4 separate times in the monitoring process, the PCM sets a cat pending code. It will also continue to check the cat for 3 drive cycles and if it sees the same condition, the code is stored in memory. If the cat is running too hot, it will also modify the trims to keep the cat within that range where the cat is best able to clean the exhaust.


On some cars, Subaru being one, the PCM uses both front and rear o2 sensors to make the fuel trim decisions even in open loop.


On the Contour, what Ford did when they remapped the PCM was lengthen the time for open loop, and change the values for the downstream o2 sensor which it was a span of .75 volt to the new .200 volt span. Usually, the cat can keep the voltage of the o2 sensor around .800-.860 (at idle), but at times it will go to .750-.850, especially if the ambient temperatures and barometric pressures are just so to make the cat cool off or heat up quicker than it can recover during a WOT or decel condition.


Carbon buildup from the engine to the cat will cause skewed fuel trims. These engines are known to carbon up easy and quickly due to the tune and driving style. It also is one of the conditions techs have to consider when "properly" diagnosing the cat and flow issues. IF there is a lack of airflow through the engine, it will run artificially rich, and the PCM will only go so far to lean it out. It will show a lean condition on the trim readings. It is something that I've seen quite a few times on cars with the Duratec 2.5 engine. A good cleanout is all it needs to restore the performance and cat function. On my car, as soon as I finished the cleanout, both cats lit up easy even after 7 years of not functioning.

 

[B3NN3TT]

This is excellent information, and I've never heard such a clear explanation of why the 0420-0430 codes are so prevalent on this platform. Thanks!

Also, I'll vouch for the water in the throttle body; I used to do it to my Saturn all the time due to chronic carbon buildup and stuck rings. It works - and it's a common procedure among Saturn 1.9 LLO engine owners. It takes A LOT of water all at once to hydrolock an engine. So unless you get entirely stupid with it, you'll be fine. And if you DO get entirely stupid with it - you deserve whatever happens to you.

 

[cclngthr]

This is excellent information, and I've never heard such a clear explanation of why the 0420-0430 codes are so prevalent on this platform. Thanks!

Also, I'll vouch for the water in the throttle body; I used to do it to my Saturn all the time due to chronic carbon buildup and stuck rings. It works - and it's a common procedure among Saturn 1.9 LLO engine owners. It takes A LOT of water all at once to hydrolock an engine. So unless you get entirely stupid with it, you'll be fine. And if you DO get entirely stupid with it - you deserve whatever happens to you.

You can flood out the engine with water without hydrolocking it, which you may want to do so the steam can get into all places in the intake and exhaust. Allowing it to remain in the engine, shut off, for 15-20 minutes is all it takes to loosen the carbon enough to throw it out the exhaust. At the same time, spraying Seafoam into the intake TB also breaks down the carbon even more. The amount of black smoke coming out of the exhaust told me the engine was basically was choked with carbon. A cat pressure test also showed less flow than it should have been. The after test showed higher flow rates in the exhaust.


Water injection is quite popular with racers and street rods. It is used to cool the intake charge to gain more power. In a diesel engine, water injection is also used to keep the intake and combustion chamber cleaner, with added power gains.

 

[amc49]

Carbon blowing water in the air 50 foot, you had me rolling on the floor with that one. Carbon mixes with water freely and easily and no effect there at ALL. They are classified as totally inert with each other on any MSDS on the planet.

Only a .... would intentionally flood out a motor with water, I've pulled engines down that did that and the rods bent. As well the more water you use the cooling effect then stops steam production more so more water is less steam. Counterproductive there. Add enough water and hot parts crack, ever heard of that????? Doesn't matter I guess if not your car that does it?

I have pulled race engines down that used water injection, what about all the steam pitting that tears up the cylinder walls, nobody EVER mentions that damage at all. Get slightly too much and you can kiss that engine bye bye in short order.

'The amount of black smoke coming out of the exhaust told me the engine was basically was choked with carbon.'

All it tells me is that you just pushed the HC level up 5 million percent right at THAT TIME ONLY. Your deduction is quite silly to me.

Typical quack thinking of the average Ford mech here and why I NEVER take a car to Ford ever to be worked on. The guys there are hacks and don't hesitate to risk damaging your car with their cockeyed theories.

 

[cclngthr]

Carbon blowing water in the air 50 foot, you had me rolling on the floor with that one. Carbon mixes with water freely and easily and no effect there at ALL. They are classified as totally inert with each other on any MSDS on the planet.

Only a .... would intentionally flood out a motor with water, I've pulled engines down that did that and the rods bent. As well the more water you use the cooling effect then stops steam production more so more water is less steam. Counterproductive there. Add enough water and hot parts crack, ever heard of that????? Doesn't matter I guess if not your car that does it?

I have pulled race engines down that used water injection, what about all the steam pitting that tears up the cylinder walls, nobody EVER mentions that damage at all. Get slightly too much and you can kiss that engine bye bye in short order.

'The amount of black smoke coming out of the exhaust told me the engine was basically was choked with carbon.'

All it tells me is that you just pushed the HC level up 5 million percent right at THAT TIME ONLY. Your deduction is quite silly to me.

Typical quack thinking of the average Ford mech here and why I NEVER take a car to Ford ever to be worked on. The guys there are hacks and don't hesitate to risk damaging your car with their cockeyed theories.

Carbon will NOT mix with water. It reacts violently to water as the carbon is broken up into smaller, and smaller pieces, especially when the carbon is very hot.


Since I did this, both cats are operating as they should. Before, both cats were not functioning, and the fuel trims made the engine run very lean. These engines are designed to produce a lot of power and do carbon up very easily. It also is a widely known issue, where the engine throws P0171 and P0174 lean codes as well as EGR insufficient P0401 codes. All of these issues make the P0420 and P0430 cat codes pop up. The ECU will not throw the lean condition code very easily, but will the cat codes because the threshold is tighter, and before the lean condition code is set.


The ideal fuel trim on any engine should be as close to 0 as possible. A positive 5% is acceptable, and any higher, the engine begins to run lean. The threshold of the cat code is 7% positive fuel trim. As the engine runs leaner, more oxygen is exiting the exhaust than the cat is capable of handling. These precats are small and can only handle so much oxygen before they start to malfunction and operate at less capacity.

 

[amc49]

The heat is what does it, I use carbon in fish aquarium filters all day long and no reaction at all. The detonation from added water helps shock it loose as well. Carbon by itself has NO reaction with water at all, look up some MSDS to find that out, clearly details its' reactivity. NONE. Carbon can be used as a filter for water. By mix I did not mean chemically rather physically, you can throw it in all day long and nothing happens.

Search the web, I found ten places saying same thing in 30 seconds..............some being chemical sites.

As well, dumping that much water in the motor could very easily shatter the cat matrix if it has the ceramic brick when the water hits that hot core. Again, if it's not your car you won't care.

You do realize that Ford had hell with many of those cats self destructing anyway to backflow lots of cat chips and bits back into engine to tear them up right? Not helping matters there at all, you might be setting it in motion. Factory mechs doing your thing there might explain some of Ford's issue with that. Lots of engines tore up there at very low mileages, my boss had one that did it.