Checking the exhaust system of a car (Mondeo 1 and 2)

Petrol engines

Start and warm up the engine to normal operating temperature and make sure the engine is running properly (ignition system is in good condition, air filter element is not clogged, etc.).

Before taking any measurements, raise the engine speed to 2500 rpm and hold it for 20 seconds. Reduce the engine speed to idle and observe the smoke coming out of the exhaust pipe. If the idle speed is too high, or if thick smoke (blue or black) comes out of the muffler for more than 5 seconds, the engine is faulty. As a rule, blue smoke indicates the presence of oil in the working mixture (engine wear), and black smoke indicates incomplete combustion (the air filter element is dirty, or the carburetor or fuel system is faulty).

Now you will need an exhaust gas analyzer suitable for measuring carbon monoxide (CO) and hydrocarbons (HC). If you do not have such a device, contact a service station.

Carbon monoxide (CO) content in exhaust gases

At the time of writing this guide, the maximum CO level at idle should not exceed 3.5% for vehicles manufactured since August 1986 and 4.5% for older vehicles.

Since January 1996, much stricter regulations (approximately 0.5%) have been introduced for cars manufactured since August 1992, equipped with a catalytic converter of exhaust gases. Such a level of CO content is difficult to achieve in case of malfunctions in the carburetor (fuel injection system) or catalytic converter, even with a good ignition system and the use of high-quality gasoline.

Hydrocarbon (HC) content in exhaust gases

Provided that the CO content is within the normal range, the HC content should not exceed 1200 pm (parts per million). If the engine does not meet these requirements at idle, the test can be repeated at a speed of approximately 2000 rpm; if the HC level is 1200 pm or less, the engine is considered to be in good working order.

Excessive HC content can be caused by oil entering the combustion chamber, but it is more likely due to incomplete combustion of the fuel.

Models with diesel engine

The only exhaust gas test applicable to diesel engines is the measurement of exhaust smoke density. The test involves accelerating the engine under no load to maximum speed, performed several times.

Note: Before starting the test, make sure that the engine camshaft drive belt is in good condition.

Excessive smoke may be caused by a dirty air filter. If not, seek professional advice.

Note: The above standards for the content of harmful substances in exhaust gases and their smoke are established in Great Britain. In Russia, these standards are regulated by GOST 17.2.3.03-87 and GOST 21393-75.

(The text was obtained in its entirety from the specified website FORDBOOK)