12PCV Valve during BACKFIRE or when the Engine is OFF.
13PCV 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 RPMdrop.
14PCV 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.
15Oil 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.
16Fuel 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.
17Older Style Evap 5) PCM controls flow to manifold 6) Vapor burns in cylinders4) Intake vacuumdraws vapor to manifold3) Fresh enters heremixes w/fuel vapor1) Fresh airenters here2) Fuel vapormoves to canister
18OBDII Evap 1 Vapor management valve. Closed when engine is off. Pulsed when engineis running.Fresh air ventcontrolled by thePCM.Closed whenengine is off.Open while engineis running.PCM monitorspressure in fueltank. Can causeDTC.
19OBDII Evap Test Mode System can be tested for leaks. VMV closed Special device pumpsnitrogen into systemto check for leaks.CVV closed
20Evaporative ServiceSome 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.
22Heated 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.
26Heated 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.
27Early 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.
28Heat Riser & EFE ValvesOld 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.
29Heat 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.
30Exhaust Gas Recirculation (EGR) Intake manifoldEGR valveSystem allows exhaustgas (water vapor) toflow from the exhaustmanifold to the intakemanifold. This coolsthe fuel mixture andreduces NOx emissions.Transfer tubeExhaust manifold
31Cooling the Air/Fuel Mixture Combustion GasesCombustion GasesWater Vapor3000º F2500° FCooling the combustion prevents formation of NOx emissions.
36Catalytic 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.
37Single bedOlder GM styleMost common construction
38Three Types of Converters Air injection tubeTwo way converter. (Single bed)Three-way converter. (Dual bed)Three-way converter with/air.flowOxidation catalystReduction catalyst
39Typical Three-Way Converter Reduction CatalystNOx reductionOxidation CatalystBurns CO & HC
40Testing 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.
41Air 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.
42Basic Parts Air Pump Hoses Diverter Check valves Metal injection tubing
43Air Pump Belt driven vane pump. Pumps fresh air into the exhaust manifold or the catalytic converter.
44Diverter ValveThe 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.