Monday, August 26th, 2013

How-to: Murder your Catalytic Converter

Catalytic Converter

Catalytic Converter

After telling you just how valuable and expensive catalytic converters are, I felt that it’s only fair to tell you how most people murder them and all of the warning signs to let you know what’s happening before they quietly lay down and die.

It’s also only fair to tell you that 90% of the time a cat’s failure is due entirely too upstream events. By upstream we mean before the converter.

Cause of Death

The first and most widely cause of death is that of poisoning. As in the human body the ingestion of foreign or inappropriate fluids or fuels will poison the inner workings of the cat, which is the catalyst of the converter, the part that makes the final cleaning process of the combustion gasses work. These poisons are very available, first on the list is leaded fuel or any lead containing additive that someone convinced you will give you more horsepower or more miles the gallon. Second on this list is water or coolant, obviously everyone knows that water will not burn and should never be in your fuel tank.

Ethanol Fuel

But with the introduction of ethanol fuel, which can legally be from 10% to 85% many fuel tanks end up with gallons of water just due to ethanol separation. Also there are always the problems within the engine such as head gasket leaks or intake manifold leaks that allow coolant to intermingle with the fuel charge mixture.

Fuel Management System

The last symptom is caused by excessive long term and short term fuel trim. Long term and short term fuel trim is notably abbreviated as ltft or stft. They ALWAYS have a suffix that reads B1 or B2 and always ending with %. Putting all of these letters in order will read as ltftb1% and a number. That reads as long term fuel trim bank 1 at (any number) %. That number can be positive or negative from 1 to 30.

If the number is a positive number and over 10% then the engine is running lean and the computer is adding fuel to make it run smoothly. Transversely if the number is a negative number above -10% then the vehicle is running too rich and the computer is subtracting fuel to aid in its efficiency.

Either way it means that the fuel management system is having a hard time maintaining the perfect air to fuel ratio and the catalytic converter will either be drowned in raw fuel or starved and be put into condition of overheating.


Destroying a Catalytic Converter

Both of these issues will turn on a check engine light and if ignored will damage the cat. Or if the check engine light has been on for some time before and ignored then you will never know that there is an underlying fuel management issue and you will damage the cat.

Oil Contamination

Oil contamination of any type will coat the catalyst and render them useless as will using any Teflon or Silicone based products on any exhaust parts or assemblies as they will contaminate the oxygen sensors and cause the miscalculation of the fuel trim.

Types of Converter Damage

Other types of converter damage are not so complicated, hitting things in the roadway or thinking that your vehicle is a 4 wheel drive pick up when it’s obviously not are always a source of converter damage. They are easily observed by their misshapen cases or rattling noises especially when the engine is revved are a sure sign that the “web” has been broken and is bouncing around.


Death by Engine Light

The last way to destroy your converter and your budget is to ignore any flashing check engine lights or fuel smells or a glow from under your vehicle or obvious exhaust leaks before the converter. This is the first sign of a severe overheating problem in the cat and if ignored long enough the ceramic substrate will melt and clog the cat. When this happens you will experience a severe loss of power and then finally the vehicle will stop and you are in SNEAKER MODE. Never, never a good place to be!

Word of Advice

Now a word of advice to all you internet researchers, I have seen videos and read stories on how to “clean” your catalytic converters. One such piece actually told people to add paint thinner to their fuel tanks or actually removing the converters and cleaning them in soap and water. Frankly these are ways to get around a code 420 catalytic efficiency issues. This will remove some of the contamination on the substrate to perhaps turn off the check engine light TEMPORARILY.

There is also a trick to burn off contaminants by causing the cat to overheat after the upstream issues have been corrected. These are very rare cases and very dangerous to not only the vehicle but also the person performing them and should NEVER be attempted by anyone without the proper training, so BEWARE!


Gregg’s Automotive Maintenance & Repair Center

236 S. Tamiami Tr.
Punta Gorda, Fl. 33950
Auto Repair, A/C Repair, Oil Change, Brake Repair & Transmission Services