Modern Automotive Technology PowerPoint for by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

Emission Control System Chapter 44 Emission Control System Testing, Service, and Repair

Contents Computer-controlled emission system service (16 Topics) Computer-controlled emission system service Emission maintenance reminder Inspecting emission control systems Exhaust gas analyzer Emissions testing programs Vacuum solenoid service

Contents PCV system service Evaporative emissions control system service Thermostatic air cleaner system service EGR system service Air injection system service Pulse air system service

Contents Catalytic converter service Oxygen sensor service Emission control information sticker OBD II drive cycle

Emission System Service Computer-Controlled Emission System Service Most emissions problems are caused by a malfunction in a system unrelated to the emission control system fuel system ignition system exhaust system computer control and electrical systems

Scanning Emission Systems Connect the scan tool to the data link connector Check for diagnostic trouble codes (DTC’s) Retrieve data

Scanning Emission Systems

Scan Tool Readout A. DTC B. Description C. Possible causes

Emission Maintenance Reminder The circuit turns on a dash light to indicate the need for emission control system service After repairs, the light must be turned off Refer to the service manual for numerous procedures

Inspect vacuum hoses and wires Inspecting Emission Control Systems Inspect vacuum hoses and wires

Inspecting Vacuum Hoses Use a stethoscope to listen for vacuum leaks

Measures the chemical content of exhaust gas Exhaust Gas Analyzer Measures the chemical content of exhaust gas

Two-Gas Analyzer Measures two gases: hydrocarbons (HC) carbon monoxide (CO)

Four-Gas Analyzer Measures four gases: hydrocarbons (HC) carbon monoxide (CO) carbon dioxide (CO2) oxygen (O2)

Five-Gas Analyzer Measures five gases: hydrocarbons (HC) carbon monoxide (CO) carbon dioxide (CO2) oxygen (O2) oxides of nitrogen (NOx)

Analyzer with a calibration gas Five-Gas Analyzer Analyzer with a calibration gas

Using a Gas Analyzer Warm-up the analyzer about 10 minutes Zero and calibrate the analyzer zero the meter while sampling shop air or calibration gas Warm the vehicle to operating temperature Insert a probe into the tail pipe through a hole in the shop’s vent hose

Analyzer Test Procedures Two speed idle test idle and 2500 rpm Dynamometer test loads the engine to simulate actual driving conditions Compare the readings to specifications

Using a Gas Analyzer

Exhaust Gas Analyzer Readings

Hydrocarbons HC Measured in parts per million (PPM) by volume Unburned gasoline Newer vehicles have specifications of approximately 220 PPM

Carbon Monoxide CO Measured in percentage (%) by volume Indicates incomplete burning of fuel or rich mixtures during combustion caused by insufficient air or excess fuel Normal readings are below 1.5%

Oxides of Nitrogen NOx Measured in parts per million (PPM) by volume Formed when nitrogen and oxygen in the cylinder combines Occurs when combustion chamber temperatures are high

Carbon Dioxide CO2 Measured in percentage (%) by volume Byproduct of normal combustion that occurs when one carbon atom combines with two oxygen atoms Readings should be high, 8–15%

Oxygen O2 Measured in percentage (%) by volume Typical readings should be 1–2% on a fuel-injected engine Needed for the catalytic converter to burn HC and CO emissions Indicator of a vehicle’s air-fuel mixture High readings indicate a lean mixture

Emissions Testing Programs Exhaust gas readings are taken idle and a set rpm (e.g. 2500 rpm) The vehicle may be checked for a catalytic converter, fuel inlet restrictor, and other emission control systems

IM 240 The vehicle is operated on a dynamometer at speeds up to 55 mph (89 kmh) for 240 seconds while exhaust gases are measured The evaporative emissions system may be tested: purge test pressure test

Purge Test Measures the flow of fuel vapors into the engine while performing the IM 240 test A flow meter is installed into the purge line between the canister and the intake manifold A computer compares the purge rate to specifications

Pressure Test Checks the system for leaks into the atmosphere Pressure test equipment is connected to the evaporative emission system A computer meters low pressure nitrogen into the system (0.5 psi, 3.4 kPa) If the pressure drops too much, the computer will fail the system

Vacuum Solenoid Service Refer to a vacuum hose diagram

Checking Solenoid Valves Check vacuum hoses for hardening, cracks, and leaks

Checking Solenoid Valves Use a multimeter to check for voltage to the solenoid

Checking Solenoid Valves Use a vacuum pump to check solenoid vent/hold

Checking Solenoid Valves

PCV System Service A faulty PCV system can increase emissions, cause engine sludging, wear, and idle quality problems A leaking system can cause lean mixture A plugged system can cause a rich mixture

PCV Maintenance Manufacturers recommend periodic maintenance Inspect hoses, grommets, fittings, and breather hoses Clean or replace the breather filter Check or replace the PCV valve

PCV Testing Remove the valve from the grommet and shake it The valve should rattle freely Start the engine and plug the valve with your finger You should feel vacuum The engine speed should drop 40–80 rpm on carbureted engines A special tester may be used

PCV Testing

PCV Test / Gas Analyzer Run the engine at idle; note the readings Pull the PCV valve out of the grommet; note the readings Compare the readings If O2 and CO do not change, the PCV system is plugged If O2 goes up more than 1% or CO goes down more than 1%, the oil may be diluted with gasoline or excess blowby

Evaporative Emissions Control System Service Symptoms: fuel odor fuel leakage fuel tank collapse excess pressure in fuel tank rough idle

Maintenance and Repair Clean or replace the canister filter when specified Inspect the fuel tank cap and pressure test it for leakage Inspect all hoses for deterioration Replace with fuel-resistant hose

Canister Filter Replacement

Use a vacuum pump to check the diaphragm or solenoid vent/hold Purge Valve Check Use a vacuum pump to check the diaphragm or solenoid vent/hold

Thermostatic Air Cleaner System Service If the flap remains in the cold air position all the time, the engine may miss and hesitate If the flap stays in the hot air position, the engine could perform poorly when at full operating temperature

Maintenance and Testing Visually inspect the following parts: hoses hot air tube exhaust manifold heat shroud sensor and vacuum motor operation

Checking Operation A. Watch the door action B. Apply vacuum to the motor

EGR System Service Symptoms: stalling at idle rough idle detonation lean mixture emissions testing NOx failure

EGR Testing Refer to a service manual Warm the engine to operating temperature Quickly increase engine speed to 2500–3000 rpm The valve pintle should move With the engine idling, apply vacuum to the valve with a hand pump The engine should miss or stall, indicating EGR flow

EGR Testing

Testing (Electronic Type) A scan tool may allow you to observe the valve status or drive the valve open manually An oscilloscope can be used to observe the solenoid drive signal or feedback signal from a pintle position sensor

Testing (Electronic Type) Oscilloscope connections

Testing (Electronic Type) Solenoid drive signal

Testing (Electronic Type) Pintle position sensor feedback signal

Air Injection System Service Symptoms: backfiring noise increased HC and CO emissions

Maintenance Replace the pump inlet filter if specified Adjust the belt tension Inspect the hoses and components

Testing Use an exhaust gas analyzer Run the engine and note the readings Disable the air injection system by pinching or disconnecting the pump discharge hose O2 should drop 2–5% HC and CO should increase If no change is noted, the system is not working

The pump should produce 2–3 psi (14–21 kPa) Pump Output Check The pump should produce 2–3 psi (14–21 kPa)

Catalytic Converter Service Problems are caused by contamination, overheating, and extended service A plugged converter can cause high exhaust back pressure and loss of power Pellet-type converters may be drained and refilled with new pellets

Plugged Catalytic Converter

Backpressure Test Install a pressure gauge in the O2 sensor hole; compare the pressure to specifications

Gas Analyzer Test Run the engine and catalytic converter to operating temperature, and note the readings If oxygen is 1–2% or more, and CO is high (above 0.5 %), the converter is not oxidizing

Converter Replacement Replace all gaskets, rubber mounts, and hardware

Oxygen Sensor Service Sensors become coated or fouled with exhaust byproducts Fuel economy and emissions may be affected A “lazy” or “dead” O2 sensor will change resistance or voltage slowly, or not at all, with changes in the exhaust gas oxygen level

Testing Connect a scan tool, check for diagnostic trouble codes Observe the O2 sensor voltage in the scan data A digital voltmeter may be used An oscilloscope may be used

Voltmeter Testing Probe between the signal wire and ground Fast-idle the engine to ensure the sensor is hot Record the minimum, maximum, and average voltages The voltage should go below 200 mV, above 800 mV, and average around 450 mV

Voltmeter Testing

Probe between the signal wire and ground Oscilloscope Testing Probe between the signal wire and ground

The sensor output should vary as shown Oscilloscope Testing The sensor output should vary as shown

Zirconia sensor waveform Oscilloscope Testing Zirconia sensor waveform

If the waveforms are too similar, it indicates a faulty converter Dual Trace Scope If the waveforms are too similar, it indicates a faulty converter

Emission Systems Wiring

O2 Sensor Replacement Disconnect the negative battery cable Unplug the sensor connector Spray the threads with penetrating oil Use a special sensor socket Inspect for contamination

O2 Sensor

Lazy sensor contaminated with carbon soot O2 Sensor Lazy sensor contaminated with carbon soot

Emission Control Information Sticker The emission control information sticker contains important engine data evaporative emissions information schematics specifications

Vehicle Emission Control Information

OBD II Drive Cycle Performed: when the ECM has been disconnected from power when the diagnostic trouble codes have been erased to verify repairs, ensuring the DTC does not reoccur before an emissions test

Each vehicle and manufacturer has its own drive cycle OBD II Drive Cycle Each vehicle and manufacturer has its own drive cycle

OBD II Drive Cycle The vehicle is driven on a road test or dynamometer To begin, coolant has to be below a specified temperature The vehicle is driven through various conditions to allow computer to monitor all specified systems