1. Emission Control
System Service

2. Unit of Study Types and Sources of Emissions Vapor Control Systems
Improvement of Combustion
Treating Exhaust Gas
Measuring Exhaust Emissions
Diagnostics

3. Three Major Pollutants
Hydrocarbons (HC) un-burnt gasoline.
Carbon monoxide (CO) partially burnt gasoline.
Oxides of Nitrogen (NOx) air burns against itself.

4. Evaporation from the fuel tank.
Blow-by gases which escape from the crankcase.
Tail pipe emissions.
Carburetor evaporation from the float bowl on old cars.

5. Three Ways to Control Pollution
Improve combustion
B. Capture the vapors and re-burn them.
C. Treat the exhaust.

6. Vapor Control
System Service

7. Positive Crankcase Ventilation (PCV)

8. Regulating the PCV Vapor Flow
Amount
Condition
Manifold
Vacuum
Blow-by
Gases
Idle
High
Small
Volume
High Speed
Low Vacuum
Large

9. PCV Valve The PCV valve has two functions: 1. To regulate the
amount of vapor
entering the intake
manifold at various
engine speeds.
2. Prevent damage
from backfire.

10. PCV Valve at Idle Speed
Idle speed

11. PCV Valve at Cruising Speed

12. PCV Valve during BACKFIRE or when the Engine is OFF.

13. PCV Service Replace PCV valve every 30,000 miles.
Clean the breather filter if applicable. The valve can be cleaned also if you don’t want to replace it.
Inspect hoses for proper routing and deterioration.
Check the air cleaner housing for oil build up.
Check PCV system function.
1) Use the PCV vacuum tester.
2) Use the tachometer and look for RPM
drop.

14. PCV Trouble-Shooting Notes
Defective PCV system can cause big time vacuum leaks. This can lead to a very fast idle speed or stalling.
If the valve or hoses get clogged the vapors back-up into the air cleaner clogging it too and puts oil in the air cleaner housing.
A strange problem is if a valve cover gasket starts leaking oil winds up in the air cleaner also.

15. Oil in Air Cleaner Housing
Gasket leaks mess up the vacuum on a PCV system.
Manifold sucks air though the leaking gasket and the blow-by backs-up into the air cleaner.

16. Fuel Tank Evaporative Controls
Captures HC evaporation from the fuel tank.
Seals the gas tank and store the vapors in a charcoal canister.
Vapor are purged to the intake manifold when the engine is running.

17. Older Style Evap 5) PCM controls flow to manifold 6) Vapor burns in
cylinders
4) Intake vacuum
draws vapor to manifold
3) Fresh enters here
mixes w/fuel vapor
1) Fresh air
enters here
2) Fuel vapor
moves to canister

18. OBDII Evap 1 Vapor management valve. Closed when engine is off.
Pulsed when engine
is running.
Fresh air vent
controlled by the
PCM.
Closed when
engine is off.
Open while engine
is running.
PCM monitors
pressure in fuel
tank. Can cause
DTC.

19. OBDII Evap Test Mode System can be tested for leaks. VMV closed
Special device pumps
nitrogen into system
to check for leaks.
CVV closed

20. Evaporative Service
Some charcoal canisters have a filter under them that needs to be replaced every 30,000 miles.
Inspect the hoses for proper routing and deterioration.
Check to gas cap.
1996 and newer cars can be tested for leaks in the system.
Use the scan tool to check the status of the purge control solenoid or control valves.

21. Controlling Combustion
System Services

22. Heated Air Intake Systems
Warms-up inlet air around exhaust manifold.
Enhances fuel evaporation for better combustion.
Maintains a 120˚F air temp.
2 types: Vacuum operated and mechanical thermostat.
Prevents throttle icing.

23. Engine COLD
Warm
air

24. Engine WARM
Warm
air
Cold air

25. Engine HOT
Cold air only

26. Heated Air Intake Service
Inspect system for proper hose routing, hose condition and connections.
Check vacuum diaphragm for proper operation.
Check blend door for proper movement.
Check thermostat for proper operation.

27. Early Fuel Evaporation (EFE)
Helps engine warm-up faster.
Uses exhaust gas to warm intake manifold.
Uses a special passageway under the intake manifold called a crossover.
Use mostly on carbureted and throttle body Vee engines.
A control valve forces the exhaust gas from one bank to the other.
Only operates during the first 5 minutes or so of operation.

28. Heat Riser & EFE Valves
Old Heat Riser valves used a bi-metal thermostatic spring to open and close the valve.
EFE Valve was vacuum operated and was controlled by a TVS.

29. Heat Riser (EFE) Service
Check exhaust valve for freedom of movement.
Check vacuum diaphragm for proper operation.
Check vacuum hoses for proper routing, condition and connections.

30. Exhaust Gas Recirculation (EGR)
Intake manifold
EGR valve
System allows exhaust
gas (water vapor) to
flow from the exhaust
manifold to the intake
manifold. This cools
the fuel mixture and
reduces NOx emissions.
Transfer tube
Exhaust manifold

31. Cooling the Air/Fuel Mixture
Combustion Gases
Combustion Gases
Water Vapor
3000º F
2500° F
Cooling the combustion prevents formation of NOx emissions.

32. EGR Valve Convention vacuum diaphragm style.
Back-pressure diaphragm type.
Electronic (solenoid)
From exhaust
To intake manifold

33. EGR Controls
EGR not necessary when the engine is cold or idling. Since NOx forms only from excessive combustion chamber temperatures.

34. EGR Service Checking valve for proper operation.
Inspect hoses for proper routing, condition and connections.

35. TREATING EXHAUST GAS
Air Injection Systems
Catalytic Converters 1

36. Catalytic Converter Converts HC, CO, NOx into H²0, CO², O² & N²
Uses rare metals to create a catalytic action.
What is a catalyst?
Single bed or two-way converters.
Dual bed or three-way converters.

37. Single bed
Older GM style
Most common construction

38. Three Types of Converters
Air injection tube
Two way converter. (Single bed)
Three-way converter. (Dual bed)
Three-way converter with/air.
flow
Oxidation catalyst
Reduction catalyst

39. Typical Three-Way Converter
Reduction Catalyst
NOx reduction
Oxidation Catalyst
Burns CO & HC

40. Testing Catalytic Converters
Visual inspection on hoist. Check heat shields, air pipes pipe integrity.
Mallet test for loose substrate.
Exhaust back-pressure test.
Temperature drop test using a pyrometer.
Cat test using the Gas Analyzer.

41. Air Pump or Air Injection Systems
Pumps fresh air into the exhaust manifold to burn up any HC or CO still present in the exhaust.
Acts as an after burner.
Needs several control valves for the system to function properly.

42. Basic Parts Air Pump Hoses Diverter Check valves
Metal injection tubing

43. Air Pump Belt driven vane pump.
Pumps fresh air into the exhaust manifold or the catalytic converter.

44. Diverter Valve
The engine will backfire on deceleration if air is pumped into the exhaust manifold.
The diverter valve sends the air back into the atmosphere during decel.

45. Diverter Normal Driving

46. Diverter During Decel

47. One-Way Check Valve Prevents damage to system in case of a backfire.
Allow air to flow into the exhaust manifold.
Blocks exhaust from going back toward air pump.

48. Air Switching Valve
Used on air management systems that integrate the air injection system and the catalytic converter.
Simply changes air from being pumped into the exhaust manifold to the converter.

49. Air Management System
Air Pump
Engine cold

50. Air Management
Engine warmed-up

51. Measuring Exhaust Emissions
4 Gas Analyzer
HC, CO, CO2, O2
5 Gas Analyzer
HC, CO, CO2, O2, NOx

52. EPA EMISSION STANDARDS
HC 900 ppm CO 9.0%
HC 800 ppm CO 8.0%
HC 700 ppm CO 7.0%
1980 HC 300 ppm CO 3.0%
1981- on HC 220 ppm CO 1.2%
I.M. 240 Test