This article reproduced by courtesy of The Automotive Technician The Automotive Technician provides practical technical information, training, case studies and diagnostic assistance to technicians challenged by new and complex technologies in the modern vehicle. nduction is the stage of the problem.There appears to be working cycle of an engine no single reason for a build-up in which the fuel and air is The next of contaminants in the intake Idrawn into the cylinders. systems, and it seems some makes and models suffer more Contamination means to plague… than others. make impure by exposure to or addition of a polluting Source of substance. INDUCTION contamination Induction contamination means any change from the original state CONTAMINATION Carbon build-up around the of the complete intake system, fuel by Jeff Smit throttle body, throttle bore and inlet or air, of a vehicle. The air intake manifold restricts the airflow into the system includes the air filter box, air filter, engine cylinders. Such an obstruction air intake hoses, throttle body or butterfly will result in a poor idle, a stalling condition unit, inlet manifold, engine valves and even and a drop in performance and fuel the cylinder bores. economy. The most common source of these deposits is from the combustion and The incidence of vehicles losing power crankcase gases. and performance because of some form of Take the inlet manifold, for example. Once, induction restriction is increasing greatly. there was a carburetor sitting on top of The combination of the gases from the TaT sees evidence of this problem through the engine. Fuel was delivered above the positive crankcase ventilation (PCV) the increasing numbers of TaT assist throttle plates, which were awash in petrol, system and from the exhaust gas requests. Some of the pictures showing one of the world’s great solvents. recirculation (EGR) system will, in most serious build-up of carbon have come cases, cause the intake contamination, So carbon could not build up because of from TaT workshops and others from our more so when the PCV and the EGR the washing action of swirling, fuel laden subscribers. points are positioned near the throttle air. plate. The EGR gases mix with the gases It raises the It’s fairly common now to find vehicles with from the PCV system to form the gummy question – what’s very dirty inlet manifolds and throttle bodies or waxy residue. bad enough to cause some components to The piston strokes and the negative to changed? stick and fail. Customers complain of a loss positive pressure pulsations direct the of power or poor fuel economy. And what do the aftermarket workshops gases towards the throttle body, where need to know? Is there a need for some Vehicles began suffering from induction they are baked on due to the intense heat. education of the motoring public? Can the contamination with the introduction of the Foreign and domestic vehicles suffer contamination trend be slowed or reversed first electronic fuel injection (EFI) systems. equally. through some preventative measures? While these systems bring many benefits, Many things are blamed for the build-up of including improved performance, fuel Engine PCV system carbon in inlet manifolds – poor fuel quality, economy and lower emission output, they are subject to intake and throttle bore The vapours that end up in an engine’s poor or incorrect engine oil, engine design crankcase contain moisture as well as and even driving styles. contamination problems. Once fuel was stopped from passing through the throttle combustion by-products and unburned Sometimes technology generates new bore, contaminants began to build up. fuel vapours. The crankcase is sealed to problems. Is the build-up of carbon in the prevent the escape of these gases into intake system one of Eventually, those carbon deposits must be the atmosphere, but the vapours must them? removed to restore engine performance. be removed to prevent oil contamination Strict environmental controls, Euro 4 that leads to sludge formation. The PCV emissions standards, and consumer system siphons these vapours from the demands for better fuel economy crankcase and routes them into the intake and performance forced design manifold so they can be reburned in the engineers to develop direct engine. injection systems for both petrol The main component in the PCV system is and diesel engines. These the PCV valve, which is usually located in systems took the introduction the valve cover. A hose connects the PCV of the fuel away from the inlet valve to the intake manifold. manifold altogether.So yet again the introduction of new and The PCV valve is spring-loaded with a supposedly better systems has specific orifice size designed to restrict the by their very design caused a spin-off amount of air siphoned from the crankcase into the intake manifold. This is necessary because air drawn There are a number of through the valve from the crankcase has a EGR system types: leaning effect on the fuel mixture, much the • Ported same as a vacuum leak. (late 1960s to present) So airflow through the valve must be • Positive backpressure controlled within certain limits. At idle, air (1970s to present) flow is reduced because little blow-by is • Negative backpressure produced. (1970s to present) When the engine is cruising and vacuum • Pulse-width modulated is high, airflow through the PCV valve is at (early 1980s to present) a maximum to purge the vapours from the • Digital–electronic crankcase. (late 1980 to early 1990s) EGR system • Linear–electronic (early 1990s to present) A chemistry lesson on NOx first. It’s the later model types The ‘x’ in NOx stands for the various that are linked with the direct change, the oxides of nitrogen that are created. injection systems which concern build-up continues. technicians today. Eventually, the Among them are: NO (nitric oxide), a build-up causes more colorless, poisonous gas; NO2 (nitrogen issues with poor performance dioxide) which is a reddish brown, toxic Symptoms of EGR and fuel economy which in turn cause gas; and N2O (nitrous oxide) which is more PCV gases. Eventually the EGR commonly known as laughing gas. malfunction valve won’t seat correctly and allows EGR Environmental imperatives will demand gases to enter the throttle body at idle and The EGR system is often misdiagnosed compound the problem. continuing control of nitrogen oxide or blamed for problems that may not be emissions. Most of the carbon monoxide its fault, including hard starting, stalling Some of the worst cases we have seen and almost 50 per cent of the nitrogen and hesitation during warm-up, rough have been on common rail diesel vehicles. oxides and hydrocarbons come from idle, missing, spark knock, backfiring and A lot has been said about the quality of burning petrol and diesel fuels in cars and loss of power. Sure, the EGR system can diesel fuel, and perhaps this is a small trucks. cause these symptoms, but so can other contributor to the problem. There have Nitrogen oxides are only created at very components and systems. Don’t jump to been issues with vehicles losing power high temperatures and pressures, as found any conclusions until you have checked and becoming barely driveable. The top in automotive engines. the basics. One common reason is carbon part of the inlet manifold is found to be build-up in the intake system. choked with carbon. In some cases the Basic EGR operation inlet manifolds have had to be replaced It appears that with the introduction because of the extent of the contamination of the Euro 4 emission standards, the NOx forms under high pressures and and damage to the manifolds. EGR system may be operating in many temperatures found in the combustion more situations than in previous models, There have been stories that some chamber, so it can be controlled by sometimes at idle. technicians have even blocked off the EGR reducing the compression or the system and fitted oil traps in the PCV lines. temperature in the combustion chamber. The build-up of contamination in the intake TaT has heard that manufacturers are system can be caused by a number of Emission control engineers chose the working on software upgrades to try and possible factors. First, the engine needs to latter. Temperature is controlled by minimise the problem, but this may not be be in good working order so that the PCV introducing a metered amount of inert gas enough. gases are as low as possible and as clean into the cylinder to partially quench the fire. as possible. This is where correct and There are many good products available The result is that the fire in the combustion regular servicing, as well as quality and which can help clean and maintain the inlet chamber is less intense. EGR exhaust correct engine and drive train oils, are very manifold. important. gas occupies space that would otherwise The BG product for both petrol and diesel contain air. It is TaT’s belief that many technicians engines is one that we know works very With EGR, the fire is more like a would claim that the servicing schedule for well, and there are no doubt others. the modern vehicle is too stretched out. smoldering pile of leaves than a blast It’s a problem which will need some furnace. Car makers have been promoting low customer education so that the clearning Exhaust gas was chosen because it is free cost service, but this has had the effect and servicing of the throttle body and inlet and plentiful. of teaching vehicle owners that they manifold are included as an important can get away with one service a year or part of every service.