1 Emission Control Systems

2 Vehicle Pollution Sources 3 areas of a vehicle that can pollute…3 areas of a vehicle that can pollute…  tailpipe emissions  fuel tank vapors (and carburetor vapors)  crankcase blow-by gases

3 Major Engine Pollutants 1) hydrocarbons: produced when some or all of the fuel does not get burned during combustion, or from raw gasoline vapors  tailpipe emission  fuel tank & carburetor emission 2) carbon monoxide: produced when there is insufficient oxygen to support combustion  tailpipe emission 3) oxides of nitrogen: produced when combustion temperatures exceed 1400°C / 2500°F  tailpipe emission

4 Blow-by Emission Control crankcase ventilation system handles blow-by gasescrankcase ventilation system handles blow-by gases  hydrocarbon emissions road-draft tube used until 1962road-draft tube used until 1962

5 Blow-by Emission Control Positive Crankcase Ventilation system (PCV system) in use since 1963Positive Crankcase Ventilation system (PCV system) in use since 1963

replace the Positive Crankcase Ventilation valve and check its hose (inexpensive)… replace the Positive Crankcase Ventilation valve and check its hose (inexpensive)… Tech Tip:Tech Tip: pull the PCV valve out of the engine while it’s running pull the PCV valve out of the engine while it’s running place your finger under the valve place your finger under the valve you should feel and hear suction & the valve should click you should feel and hear suction & the valve should click 6 Checking PCV System

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8 Fixed Orifice Tube PCV Systems a precisely determined hole size acts as the valvea precisely determined hole size acts as the valve no need for a spring and valve assemblyno need for a spring and valve assembly

9 Evaporative Emission Control System prevents raw HC’s (from gasoline) from being vented into the atmosphereprevents raw HC’s (from gasoline) from being vented into the atmosphere  (in use since 1971) charcoal canister absorbs fuel vapors when the engine is off & sends them to the intake manifold so they can be burned when the engine is runningcharcoal canister absorbs fuel vapors when the engine is off & sends them to the intake manifold so they can be burned when the engine is running

10 Evaporative Emission Control Systems on 1996 & newer vehicles, PCM…on 1996 & newer vehicles, PCM…  purges canister vapors via a purge solenoid  monitors vapor flow  monitors the system for leaks  vehicle may use a separate pump to pressurize system to see if pressure can be maintained  if PCM detects a leak, check engine light will illuminate

11 some canisters have filters that need periodic replacement…some canisters have filters that need periodic replacement…

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13 Reducing NOx Tailpipe Emissions Exhaust Gas Recirculation valve (EGR) allows some exhaust gas back into the intake air streamExhaust Gas Recirculation valve (EGR) allows some exhaust gas back into the intake air stream  used on most engines since mid-1970’s but not all EGR dilutes/displaces fresh, incoming AFM which drops combustion temperature = < NOxEGR dilutes/displaces fresh, incoming AFM which drops combustion temperature = < NOx

14 EGR typically operates under light throttle, cruising conditions on a warmed up engineEGR typically operates under light throttle, cruising conditions on a warmed up engine during warm up, WOT & at idle, it does not operateduring warm up, WOT & at idle, it does not operate EGR Valve EGR Pipe

15 EGR Valve Styles 1) mechanical EGR operated by engine vacuum1) mechanical EGR operated by engine vacuum  vacuum acts on a diaphragm to open the valve (fig. a)  some EGR valves use a computer controlled solenoid to modulate the vacuum signal to the diaphragm (fig. b)  others use an exhaust pressure sensor to help determine rate of exhaust gas flow (fig. c) fig. a fig. b fig. c

16 EGR Valve Styles 2) digital or electronic EGR valve2) digital or electronic EGR valve  PCM controls 1 or more solenoids to modulate EGR flow  no vacuum diaphragm is used  each solenoid has an integral pintle position sensor  this sensor “tells” the PCM the position of the pintle valve  the solenoids are pulsed on & off by the PCM many times/second when needed

17 EGR Service Inoperative EGR systems can lead to…Inoperative EGR systems can lead to…  excessive NoX emissions (possible failure at AirCare)  detonation (knocking & pinging) caused by…caused by…  defective diaphragm  weak vacuum signal defective or incorrectly routed vacuum hoses defective or incorrectly routed vacuum hoses  shorted or open solenoid  exhaust passage blocked with carbon

18 EGR Service Excessive EGR operation can lead to…Excessive EGR operation can lead to…  rough idle  stalling caused by…caused by…  improperly routed vacuum hoses  carbon on pintle valve seat  faulty EGR valve

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20 Reducing Tailpipe Emissions catalytic converters reduce HC, CO & possibly NOxcatalytic converters reduce HC, CO & possibly NOx  used on all vehicles since mid-1970’s HC & CO in the exhaust is oxidized by the catalyst which can contains platinum, palladium & rhodiumHC & CO in the exhaust is oxidized by the catalyst which can contains platinum, palladium & rhodium HC + O 2 = CO 2 & H 2 0HC + O 2 = CO 2 & H 2 0 CO = CO2CO = CO2 this is a two-way catalystthis is a two-way catalyst needs ≈ 315°C / 600°F to operateneeds ≈ 315°C / 600°F to operate

21 Three Way Catalysts reduces HC, CO and NOx levelsreduces HC, CO and NOx levels NOx is converted to nitrogen & CO 2NOx is converted to nitrogen & CO 2 front ½ controls NOx & back ½ reduces HC & COfront ½ controls NOx & back ½ reduces HC & CO  contains cerium – has the ability to store oxygen  the oxygen is used to oxidize HC & CO in use in Canada since 1988in use in Canada since 1988

22 Reducing Tailpipe Emissions air injection systemsair injection systems  used on some engines, but not all cold engine: air is injected into the exhaust manifold to oxidize HC & COcold engine: air is injected into the exhaust manifold to oxidize HC & CO warm engine: air is injected into the converter to oxidize HC & COwarm engine: air is injected into the converter to oxidize HC & CO

23 Air Injection Systems

24 Causes of excessive hydrocarbons…

25 Causes of Excessive Carbon Monoxide… plugged air filterplugged air filter high float levelhigh float level choke not openingchoke not opening faulty fuel injectorfaulty fuel injector higher than normal fuel pressurehigher than normal fuel pressure faulty EFI sensorfaulty EFI sensor

26 Causes of Excessive NOx… carbon depositscarbon deposits inoperative EGR valveinoperative EGR valve  some valves are vacuum operated  others are electronically activated higher than normal coolant temperatureshigher than normal coolant temperatures

27 Pollution Sources & What Controls Them – a Recap… 3 areas of a vehicle that can pollute…3 areas of a vehicle that can pollute…  tailpipe emissions  fuel tank vapors (and carburetor vapors)  crankcase blow-by gases