Chapter 62

[object Object],[object Object],[object Object],[object Object],OBJECTIVES: After studying Chapter 62, the reader should be able to: Continued

[object Object],[object Object],[object Object],OBJECTIVES: After studying Chapter 62, the reader should be able to:

[object Object],[object Object],KEY TERMS: Continued

[object Object],KEY TERMS: Continued

SMOG ,[object Object],NOTE: Although upper-atmospheric ozone is desirable because it blocks out harmful ultraviolet rays from the sun, ground-level ozone is considered to be unhealthy smog. ,[object Object]

[object Object],[object Object],Figure 62–1 Notice the reddish-brown haze that is often over many major cities.

EXHAUST GAS RECIRCULATION SYSTEMS ,[object Object],Continued

Figure 62–2 When the EGR valve opens, exhaust gases flow through the valve and into passages in the intake manifold. Continued

Figure 62–3 A vacuum-operated EGR valve. The vacuum to the EGR valve is computer controlled by the EGR valve control solenoid. ,[object Object],The gas is sent from the EGR valve to openings in the manifold. On inline-type engines, an external tube is generally used to carry exhaust gas to the EGR valve. This tube is often designed to be long so the exhaust gas is cooled before it enters the EGR valve. Continued

[object Object],Continued ,[object Object],[object Object],[object Object],NOTE: EGR amount is subtracted from mass airflow calculations. While the EGR gases do occupy space, they do not affect the air–fuel mixture.

[object Object],Continued On each exhaust stroke, the engine emits an exhaust “pulse.” Each pulse represents a positive pressure. Behind each pulse is a small area of low pressure.

[object Object],Continued ,[object Object],[object Object],NOTE: The installation of a low-restriction exhaust system could prevent the proper operation of the backpressure-controlled EGR valve.

[object Object],Find the Root Cause Figure 62–4 An EGR valve position sensor on top of an EGR valve. The pintle position sensor provides a voltage output to the PCM, which increases as the duty cycle increases, allowing the PCM to monitor valve operation. Always check for a restricted exhaust whenever replacing a failed EGR valve sensor. The top of the valve contains a vacuum regulator and EGR pintle-position sensor in one assembly sealed inside a nonremovable plastic cover.

[object Object],Figure 62–5 A General Motors linear EGR valve. Figure 62–6 The EGR value pintle is pulse-width modulated and a three-wire potentiometer provides pintle-position information back to the PCM.

OBD-II EGR MONITORING STRATEGIES ,[object Object],Continued

Figure 62–7 A DPFE sensor and related components. Continued

Continued See the chart on Page 745 of your textbook.

[object Object],Figure 62–8 An OBD-II active test. The PCM opens the EGR valve and then monitors the MAP sensor and/or engine speed (RPM) to meet acceptable values. Continued Continued If signal value falls outside acceptable value in the look- up table, a DTC sets.

DIAGNOSING A DEFECTIVE EGR SYSTEM ,[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Watch Out for Carbon Balls!

[object Object],The Blazer Story This vehicle was equipped with an EGR valve-control solenoid, called an electronic vacuum regulator valve or EVRV by GM. The computer pulses the solenoid to control the vacuum that regulates the operation of the EGR valve. The tech checked the service manual for details on how the system worked, and discovered that vacuum should be present at the EGR valve only when the gear selector indicates a drive gear (drive, low, reverse). Because the tech discovered the vacuum at the solenoid to be leaking, the solenoid was obviously defective and required replacement. After replacement of the solenoid (EVRV), the hesitation problem was solved.

[object Object],Continued ,[object Object],[object Object]

[object Object],To quickly and easily remove carbon from exhaust passages, cut a 1-foot (30-cm) length from stranded wire, such as garage door guide wire or old speedometer cable. Flare the end and place the end of the wire into the passage. Set your drill on reverse, turn it on, and the wire will pull its way through the passage, cleaning as it goes, like a snake in a drain pipe. Some vehicles, such as Hondas, require that plugs be drilled out to gain access to EGR passages, shown here. The Snake Trick Figure 62–9 Removing the EGR passage plugs from the intake manifold on a Honda.

CRANKCASE VENTILATION ,[object Object],Continued

[object Object],Figure 62–10 A PCV valve shown in a cutaway valve cover showing the baffles that prevent liquid oil from being drawn into the intake manifold. Continued Oil/vapor or oil/water separators are used in some systems instead of a valve or orifice, particularly with turbocharged and fuel-injected engines. This lets oil condense and drain back into the crankcase and accumulates moisture to prevent it from freezing during cold engine starts.

PCV VALVES ,[object Object],Continued Figure 62–11 Spring force, crankcase pressure, and intake manifold vacuum work together to regulate the flow rate through the PCV valve. The flow rate is determined by the size of the plunger and the holes inside the valve. PCV valves usually are located in the valve cover or intake manifold.

Figure 62–12 Air flows through the PCV valve during idle, cruising, and light-load conditions. ,[object Object],Continued

Figure 62–13 Air flows through the PVC valve during acceleration and when the engine is under a heavy load. ,[object Object],Figure 62–14 PCV value operation in the event of a backfire.

ORIFICE-CONTROLLED SYSTEMS ,[object Object],Continued

[object Object],The Whistling Engine

PCV SYSTEM DIAGNOSIS ,[object Object],Continued

[object Object],Check for Oil Leaks With the Engine Off

[object Object],Continued NOTE: Use care on some overhead camshaft engines. With the engine running, oil may be sprayed from the open oil-fill opening. Hold a 3 × 5 card over the opening (a dollar bill or any other piece of paper can be used for this test). ,[object Object],[object Object]

[object Object],Continued Crankcase Vacuum Test The PCV system can be checked by testing for weak vacuum at the dipstick tube using an inches-of-water manometer or gauge as follows: Step #1 Remove the oil-filler cap and cover the opening. Step #2 Remove the oil-level indicator (dipstick). Step #3 Connect a water manometer or gauge to the dipstick tube. Step #4 Start engine and observe the gauge at idle and 250 RPM.

Figure 62–15 Using a gauge that measures vacuum in units of inches of water to test the vacuum at the dipstick tube, being sure that the PCV system is capable of drawing a vacuum on the crankcase (28 inches of water equals 1 psi or about 2 in. Hg of vacuum). ,[object Object],Continued

PCV MONITOR ,[object Object],Continued Figure 62–16 Most PCV valves used on newer vehicles are secured with fasteners, which makes it more difficult to disconnect and thereby less likely to increase emissions.

AIR PUMP SYSTEM ,[object Object],Continued NOTE: This system is commonly called AIR , meaning air injection reaction . Therefore, an AIR pump does pump air. The AIR pump, sometimes referred to as a smog pump or thermactor pump , is mounted at the front of the engine and driven by a belt from the crankshaft pulley. It pulls fresh air in through an external filter and pumps the air under slight pressure to each exhaust port through connecting hoses or a manifold.

Figure 62–17 A typical belt-driven AIR pump. Air enters through the revolving fins behind the drive pulley. The fins act as an air filter because dirt is heavier than air and therefore the dirt is deflected off of the fins at the same time air is being drawn into the pump. ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Continued

AIR DISTRIBUTION MANIFOLDS AND NOZZLES ,[object Object],Continued ,[object Object],Air is delivered to the exhaust system in one of two ways: ,[object Object]

Figure 62–18 (a) When the engine is cold and before the oxygen sensor is hot enough to achieve closed-loop, the airflow from the air pump is directed to the exhaust manifold(s) through the one-way check valves which keep the exhaust gases from entering the switching solenoids and the pump itself. Continued

Figure 62–18 (b) When the engine achieves closed-loop, the air is directed to the catalytic converter. Continued NOTE: These check valves commonly fail, resulting in excessive emissions (CO especially). When the check valve fails, hot exhaust can travel up and destroy the switching valve(s) and air pump itself.

[object Object],Continued ,[object Object],[object Object],[object Object]

[object Object],Figure 62–19 A typical electric motor-driven AIR pump. This unit is on a Chevrolet Corvette and only works when the engine is cold. Continued Helps warm up the three-way catalytic converters quickly on engine start-up so conversion of exhaust gases may occur sooner. The PCM turns on the AIR pump by providing ground to complete the circuit which energizes the pump solenoid relay.

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],The AIR system is disabled under the following conditions:

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],The diagnostic trouble codes P0410 and/or P0418 set if there is a malfunction in the following components:

[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],If the HO 2 S voltage does not remain low when the AIR pump is enabled, inspect for the following:

[object Object],SECONDARY AIR INJECTION SYSTEM DIAGNOSIS Continued See the chart on Page 751 of your textbook.

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object]

See the chart on Page 751 of your textbook.

[object Object],CATALYTIC CONVERTERS Continued Figure 62–20 Most catalytic converters are located as close to the exhaust manifold as possible as seen in this display of a Chevrolet Corvette. As much exhaust heat as possible must be retained for effective operation. The nearer it is to the engine, the better.

CERAMIC MONOLITH CATALYTIC CONVERTER ,[object Object],Figure 62–21 A typical catalytic converter with a monolithic substrate. The substrate is then coated with a porous aluminum material called the washcoat . Catalytic materials are applied on top of the washcoat. Continued

Figure 62–22 The three-way catalytic converter first separates the NOx into nitrogen and oxygen and then converts the HC and CO into harmless water (H2O) and carbon dioxide (CO2). ,[object Object],Continued

[object Object],Continued Some vehicles use a small, quick-heating oxidation converter called a preconverter , pup , or mini - converter that connects directly to the exhaust manifold outlet. They were often called light - off converters , or LOC . The oxidation reaction started in the LOC is completed by the larger main converter under the passenger compartment.

[object Object],OBD-II CATALYTIC CONVERTER PERFORMANCE Continued

Figure 62–23 The OBD-II catalytic converter monitor compares the signals of the upstream and downstream O2Ss to determine converter efficiency. Continued

CONVERTER-DAMAGING CONDITIONS ,[object Object],Continued ,[object Object]

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Can a Catalytic Converter Be Defective Without Being Clogged?

DIAGNOSING CATALYTIC CONVERTERS ,[object Object],Continued

NOTE: An adapter can be easily made by inserting a metal tube or pipe. A short section of brake line works great. The pipe can be brazed to the oxygen sensor housing or it can be glued with epoxy. An 18-millimeter compression gauge adapter can also be adapted to fit into the oxygen sensor opening. Figure 62–24 A backpressure tool can be made by using an oxygen sensor housing and using epoxy or braze to hold the tube to the housing. Continued

Figure 62–25 The temperature of the outlet should be at least 10% hotter than the temperature of the inlet. If a converter is not working, the inlet temperature will be hotter than the outlet temperature. ,[object Object],Continued

[object Object],Continued ,[object Object],[object Object],[object Object],Catalytic Converter Efficiency Tests The efficiency of a catalytic converter can be determined using an exhaust gas analyzer.

[object Object],Continued ,[object Object],[object Object],[object Object],NOTE: If the engine is extremely efficient, the converter may not have any excessive unburned hydrocarbons or carbon monoxide to convert! In this case, a spark plug wire could be grounded using a vacuum hose and a test light to create some unburned hydrocarbon in the exhaust. Do not ground out a cylinder for longer than 10 seconds or the excessive amount of unburned hydrocarbon could overheat and damage the converter.

OBD-II CATALYTIC CONVERTER MONITOR ,[object Object],Continued

[object Object],Aftermarket Catalytic Converters

[object Object],CATALYTIC CONVERTER REPLACEMENT GUIDELINES Continued ,[object Object],[object Object]

[object Object],[object Object],Continued See the chart on Page 755 of your textbook.

[object Object],[object Object],Catalytic Converters are Murdered “ Catalytic converters do not commit suicide—they’re murdered.”

EVAPORATIVE EMISSION CONTROL SYSTEM ,[object Object],Continued

[object Object],Figure 62–26 A typical bayonet-type gas cap. Continued If a sealed cap is used on an EVAP system that requires a pressure-vacuum relief design, a vacuum lock may develop in the fuel system.

[object Object],When Filling My Fuel Tank, Why Should I Stop When the Pump Clicks Off? If extra fuel is forced into this expansion volume, liquid gasoline can be drawn into the charcoal canister. This liquid fuel can saturate the canister and create an overly rich air–fuel mixture when the canister purge valve is opened during normal vehicle operation. This extra-rich air–fuel mixture can cause the vehicle to fail an exhaust emissions test, reduce fuel economy, and possibly damage the catalytic converter. To avoid problems, simply add fuel to the next dime’s worth after the nozzle clicks off. This will ensure that the tank is full, yet not overfilled.

[object Object],HOW THE EVAPORATIVE CONTROL SYSTEM WORKS Figure 62–27 A charcoal canister can be located under the hood or underneath the vehicle. Continued

[object Object],Figure 62–28 The evaporative emission control system includes all of the lines, hoses, and valves, plus the charcoal canister. Continued Adsorption attaches the fuel vapor molecules to the carbon surface. This attaching force is not strong, so the system purges the vapor molecules quite simply by sending a fresh airflow through the charcoal. NOTE: V ehicles with large or dual fuel tanks may have dual canisters.

Figure 62–29 A typical evaporative emission control system. Note that when the computer turns on the canister purge solenoid valve, manifold vacuum draws any stored vapors from the canister into the engine. Manifold vacuum also is applied to the pressure control valve. When this valve opens, fumes from the fuel tank are drawn into the charcoal canister and eventually into the engine. When the solenoid valve is turned off (or the engine stops and there is no manifold vacuum), the pressure control valve is spring-loaded shut to keep vapors inside the fuel tank from escaping to the atmosphere. Continued

[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],NONENHANCED EVAPORATIVE CONTROL SYSTEMS Continued

ENHANCED EVAPORATIVE CONTROL SYSTEM ,[object Object],Continued NOTE: Chrysler says that a 0.020-in.-diameter leak in an EVAP system can yield an average of about 1.35 grams of HC per mile driven.

[object Object],[object Object],Continued All vehicles built after 1995 have enhanced evaporative systems that have the ability to detect purge flow and system leakage. If either of these two functions fails, the system is required to set a diagnostic trouble code and turn on the MIL light.

[object Object],Problems After Refueling? Check the Purge Valve When refueling, this would result in a lot of fumes being forced into the intake manifold and as a result would cause a hard-to-start condition after refueling. This would also result in a rich exhaust and likely black exhaust when first starting the engine after refueling. While the purge solenoid is usually located under the hood of most vehicles and is less subject to rust and corrosion than the vent valve, it can still fail.

LEAK DETECTION PUMP SYSTEM ,[object Object],Continued The system works as follows: ,[object Object],[object Object]

[object Object],[object Object],Continued

[object Object],[object Object],[object Object],[object Object]

ONBOARD REFUELING VAPOR RECOVERY ,[object Object],[object Object]

STATE INSPECTION EVAP TESTS ,[object Object],Continued

Figure 62–30 A leak detection pump (LDP) used on some Chrysler vehicles to pressurize (slightly) the fuel system to check for leaks. Continued

DIAGNOSING THE EVAP SYSTEM ,[object Object],Continued ,[object Object],[object Object]

[object Object],HINT: To help pass the evaporative section of an enhanced emissions test, arrive at the test site with less than a half-tank of fuel. This means that the rest of the volume of the fuel tank is filled with air. It takes longer for the pressure to drop from a small leak when the volume of the air is greater compared to when the tank is full and the volume of air remaining in the tank is small. The system is typically pressurized with nitrogen, a nonflammable gas that makes up 78% of our atmosphere. The pressure in the system is then shut off and the pressure monitored. If the pressure drops below a set standard, then the vehicle fails the test. This test determines if there is a leak in the system.

LOCATING LEAKS IN THE SYSTEM ,[object Object],Figure 62–31 Some vehicles will display a message if an evaporative control system leak is detected that could be the result of a loose gas cap. Continued

[object Object],Figure 62–32 To test for a leak, this tester was set to the 0.020-inch hole and turned on. The ball rose in the scale on the left and the red arrow was moved to that location. If when testing the system for leaks, the ball rises higher than the arrow, then the leak is larger than 0.020. If the ball does not rise to the level of the arrow, the leak is smaller than 0.020 inch. After it has been determined that a leak exists and that it is larger than specified then there are two methods that can be used to check for leaks in the evaporative system. Continued

[object Object],Figure 62–33 This unit is applying smoke to the fuel tank through an adapter and the leak was easily found to be the gas cap seal. Continued

[object Object],Figure 62–34 An emission tester that uses nitrogen to pressurize the fuel system. Continued

EVAPORATIVE SYSTEM MONITOR ,[object Object],[object Object],[object Object],Continued

[object Object],Figure 62–35 The fuel tank pressure sensor (black unit with three wires) looks like a MAP sensor and is usually located on top of the fuel pump module (white unit). If the rate exceeds PCM-stored values, a leak greater than or equal to the OBD-II standard of 0.040 in. (1.0 mm) or 0.020 in. (0.5 mm) exists. The fuel tank pressure sensor is often the same part as the MAP sensor, and instead of monitoring intake manifold absolute pressure, it is used to monitor fuel tank pressure.

[object Object],Tighten the Cap Correctly Figure 62–36 This Toyota cap has a warning, the check engine light will come on if not tightened until one click. Therefore, if a P0440 or similar DTC is set, check the cap. Many diagnostic trouble codes (DTCs) are set because the gas cap has not been properly installed. To be sure a screw-type gas cap is properly sealed, tighten the cap until it clicks three times. The clicking is a ratchet device and the clicking does not harm the cap.

TYPICAL EVAP MONITOR ,[object Object],Continued ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

[object Object],Continued 1. Weak Vacuum Test ( P0440 — large leak ) Identifies gross leaks. During the monitor, the vent solenoid is closed and the purge solenoid is duty cycled. The FTP should indicate a vacuum of approximately 6 to 10 in. H 2 O. 2. Small Leak Test ( P0442 — small leak ) After the large leak test passes, the PCM checks for a small leak by keeping the vent solenoid closed and closing the purge solenoid. The system is now sealed. PCM measures change in FTP voltage over time.

[object Object],Keep the Fuel Tank Properly Filled Figure 62–37 The fuel level must be above 15% and below 85% before the EVAP Monitor will run on most vehicles.

SUMMARY ,[object Object],[object Object],[object Object],[object Object],Continued

SUMMARY ,[object Object],[object Object],[object Object],[object Object],Continued ( cont. )

SUMMARY ,[object Object],[object Object],[object Object],Continued ( cont. )

SUMMARY ,[object Object],[object Object],[object Object],[object Object],( cont. )

Chapter 62

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Chapter 62