A Contaminated EGR valveA Contaminated Intake Manifold
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Induction contamination is a relatively new phenomenon brought about by the advent of two different technologies, both of which make our cars more efficient, cheaper to run and cleaner burning for the environment. The first of these technologies is fuel injection, and the second is the various emision systems fitted to cars to eliminate noxious gases from the exhaust.
The induction system on a car includes the air filter, intake manifold, plenum chamber, cylinder head intake ports, throttle body, EGR valve and any piping or hoses that connect those components together, on some vehicles the system also includes a turbocharger.
The problem is the build up of a black sticky carbon substance on the inside walls of the induction system which causes driveability and efficiency problems for the vehicle.

The Emision Systems

The contamination of the induction system comes about by the introduction of various contaminants from the emision systems and in the case of a turbocharged car, slight leakage from the turbo seal can also enter the induction stream. Emision systems include the PCV valve (Positive Crankcase Ventilation) which scavenges 'blow by' gases from inside the engine and introduces them into the induction stream to be reburnt in the combustion process and therefore neutralised. In the past (pre-emision system days) 'blow by' gases were just vented directly into the atmosphere and the older and more worn the engine became, the more gases were produced. All engines produce 'blow by' gas which is the fuel/air mixture which escapes past the piston rings and as the gases pass through the engine they also pick up micro droplets of oil. The older and more worn the engine becomes then there is a subsequent increase in 'blow by' gas.

An EGR Valve Heavily ContaminatedAn EGR Valve Heavily Contaminated

The second emision system most cars have is the EGR system (Exhaust Gas Reticulation). The exhuast gas that your car produces is a mixture of various gases including very toxic nitrous oxides. These nitrous oxides are formed by the extreme heat built up in the combustion process when the spark ignites the fuel/air mixture inside the combustion chamber. In the past these oxides passed through the exhuast system and escaped into the atmosphere. Research has found that reducing the temperature in the combustion chamber can result in a large reduction in nitrous oxides this is the reason for the EGR system. Just as when you blow into a fire the flames burn hotter with the extra oxygen that you provided, the more oxygen that takes part in the combustion process the hotter the resulting combustion. By replacing some of that oxygen with an inert gas the temperature can be reduced and therefore the production of nitrous oxides reduced. The best supply of an inert gas is the exhuast and it is some of the exhuast gases that are fed back into the induction stream by the EGR system to replace some of the oxygen. Together with a catalytic converter in the exhaust, nitrous oxides can be reduced by 80% - 90% and some claims of 99% have been made.

The Fuel Injection System

In the days prior to electronic fuel injection, induction systems were still subjected to contamination through early rudimentary breather systems and in fact the PCV system has been around for a long time, but they did not suffer from the build-up of contamination because at the very start of the induction system there was a carburettor. The carburettor's job was to mix atomised petrol(one of the worlds best solvents) with air, that petrol/air mixture would swirl through the induction system on it's way to the combustion chamber cleaning anything in it's way. The difference with fuel injection is that the carburettor has been replaced by some injectors that mix the petrol with the air at the end of the induction system therefore depriving that system of it's 'solvent wash'.

The End Result

The end result is that as these contaminants are allowed to enter the induction stream (for very good reasons) and as there is no longer a solvent wash to keep the system clean, contaminants are able to build up in the induction system to the point where they can have a serious effect on our cars performance. Symptoms include lack of performance, increased fuel use and erratic idle.
Here at Critchley Automotive we can assess your level of contamination and advise on a solution, usually we would recommend the application of a solvent based cleaner fed into the induction system via a special spray atomiser. As the vehicle ages it will need to be cleaned more often, perhaps as a part of the routine service or maintainence for your car.
For any queries about induction contamination ring 09 2981363 and ask for Darryl or Andrew. We would be happy to assist you.