The catalytic converter
on your vehicle is an emissions component that is designed to eliminate pollutants
that are left over from combustion. Pollutants such as Nitrogen Oxides, (Nox), Hydrocarbons,
(HC), and Carbon Monoxide, (CO), are reduced to extremely low levels as they pass
through the converter‘s honeycomb inside. Thus, it reduces the harmful pollutants
from entering the atmosphere. A faulty converter will usually cause a
rough engine idle
poor fuel mileage
, and a
loss of power
at higher speeds.
When the vehicle is operating properly, the converter is able to function with
little effort. However, excessive
, poor or
(fouled spark plugs), a burnt or leaking exhaust valve, a faulty
, low engine compression
and other items can cause the converter to fail. Please keep in mind, a converter
can fail without being plugged and they can be easily checked. A plugged converter,
usually caused by overheating
and can be accompanied by loss of engine power output.
The catalytic converter has a large temperature range of operation. Most will
not begin to operate until they reach between 400 to 600 degrees Fahrenheit. From
there, normal operation can be upwards of 1,600 degrees Fahrenheit. The higher the
temperature goes is usually the result of additional pollutants in the
. If the engine is running
poorly enough and the converter’s temperature soars much higher, it can cause the
internal honeycomb itself to begin to melt and create a partially or totally plugged
A simple test for this is to simply drive the vehicle until it is at normal operating
temperature and inspect the converter. Often times they become so hot, they glow
red. Also, the insides can become loose, identified by a
, and can cause a partial blockage. Before
we start park your car on a smooth flat surface with the emergency brake on, while
the car is in park. The engine will need to be at operating temperature so wear
gloves, protective clothing and eye wear.
How to Test a Catalytic Converter Efficiency
Tools and Supplies Needed to Complete this Test
1. Temperature probe -
Infrared IR Meter
2. Creeper (A low flat board with wheels used to lay on to get under the car
Step 1 - After driving the car for at least 15 minuets park the vehicle on a
level surface, apply the parking brake,
start the engine
, and allow it
Step 2 - Using a temperature probe (infrared meter), check the difference in
exhaust temperature at both the inlet and outlet of the converter. The temperature
exiting the converter should be around 30 to 100 degrees Fahrenheit hotter. On older
vehicles with carburetor, the temperature difference will be closer to 100 degrees
Step 3 - If the temperature doesn’t change, the converter could be bad inside.
To check, shut off the engine and allow the exhaust to cool. Once cooled remove
the catalytic convert and inspect. If the honey comb is broken out the converter
has failed and needs replacing.
How to Test for a Plugged Catalytic Converter
Tools and Supplies Needed to Complete this Job
1. Vacuum gauge
3. Needle Nose Pliers
Step 1 - Attach a vacuum gauge to a vacuum port on the intake.
Step 2 - Start the engine and check the intake vacuum. That is your baseline.
Normal pressure should be between 15 and 22 inches of vacuum.
Step 3 - Rev the engine to 2,500 RPM’s. There should be a brief time that the
pressure drops, but it should return to nearly the baseline pressure you had at
idle within a few seconds.
Step 4 - Keep the engine at 2,500 RPM’s and watch the vacuum gauge. If it is
low or continues to drop, that is a good indication that there is a blockage in
the exhaust system causing back pressure to build. The most likely problem is the
It is important to mention that a faulty converter is usually caused by something
other than the converter itself. Therefore, it is important to determine what caused
the problem. Otherwise, you will be replacing a new converter soon after it is installed.
By J. Feliciani.
The exhaust system in your vehicle is designed to release exhaust gases from the
engine to the rear of the car. This system is designed to have about 3 pounds of
exhaust back pressure under heavy throttle. This means the engine should not have
to push more than 3 pounds of pressure to release the exhaust at any given time.
If a catalytic converter plugs or breaks apart it will plug the exhaust system causing
engine surging, low power and stalling. Because of the extreme temperatures the
catalytic converter produces the catalyst material can crack and break apart clogging
the outlet port of the converter causing low power and stalling.
Article first published 2016-02-03