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Pulse-air system - general information
Emissions control systems / Pulse-air system - general information


General information
1 This system consists of the pulse-air solenoid valve, the pulse-air valve itself, contained in the filter housing, and the piping - see illustration 2.1A. It injects filtered air directly into the exhaust ports, using the pressure variations in the exhaust gases to draw air through from the filter housing; air will flow into the exhaust only when its pressure is below atmospheric. The pulse-air valve can allow gases to flow only one way, so there is no risk of hot exhaust gases flowing back into the filter.

2 The systemТs primary function is raise exhaust gas temperatures on start-up, thus reducing the amount of time taken for the oxygen sensor and catalytic converter to reach operating temperature. Until this happens, the system reduces emission of unburned hydrocarbon particles (HC) and carbon monoxide (CO) by ensuring that a considerable proportion of these substances remaining in the exhaust gases after combustion are burned up, either in the manifold itself or in the catalytic converter.

3 To ensure that the system does not upset the smooth running of the engine under normal driving conditions, it is linked by the pulse-air solenoid valve to the ECU, so that it only functions during engine warm-up, when the oxygen sensor is not influencing the fuel/air mixture ratio.

Checking
4 Poor idle, stalling, backfiring and poor driveability can be caused by a fault in the system.

5 Inspect the vacuum pipe/hose connected between the filter housing and the solenoid valve for kinks, leaks and cracks along its entire length. Repair or renew as necessary.

6 Inspect the filter housing and piping. If either is cracked or damaged, renew it.

7 If the pulse-air solenoid valve is thought to be faulty, unplug its electrical connector and disconnect its vacuum hoses. Connect a battery directly across the valve terminals, and check that air can flow through the valve passages when the solenoid is thus energised, and that nothing can pass when the solenoid is not energised. Alternatively, connect an ohmmeter to measure the resistance across the valve terminals, and compare this reading to the one listed in the Specifications Section at the beginning of this Chapter. Renew the solenoid valve if it is faulty.

8 Further testing should be left to a dealer service department.

Component renewal
Pulse-air solenoid valve Note: This component can be identified by its smaller top and its clip fastening. Do not confuse it with the adjacent EGR solenoid valve, especially when reconnecting vacuum hoses.

9 Disconnect the battery negative (earth) lead - see Section 1 of Chapter 5.

10 Remove the air mass meter and resonator - refer to Chapter 4. If better access is required, remove the plenum chamber also (see illustration).

7.10 Pulse-air solenoid valve (arrowed) is located on bulkhead mounting
7.10 Pulse-air solenoid valve (arrowed) is located on bulkhead mounting bracket. It can be identified by its smaller top and its clip fastening - do not confuse it with the adjacent EGR solenoid valve

11 Releasing its wire clip, unplug the electrical connector, then use a small screwdriver to release the clip securing the valve to the bulkhead mounting bracket.

Withdraw the valve, then label and disconnect the two vacuum hoses.

12 Refitting is the reverse of the removal procedure; ensure that the hoses are correctly reconnected.

Pulse-air filter housing Note: This component, and those around it, will be very hot when the engine is running.

Always allow the engine to cool down fully before starting work, to prevent the possibility of burns.

13 Raise the front of the vehicle, and support it securely on axle stands. Disconnect the vacuum hose from the base of the filter housing (see illustration).

7.13 Disconnect vacuum hose from base of pulse-air filter housing . . .
7.13 Disconnect vacuum hose from base of pulse-air filter housing . . .

14 Disconnect the battery negative (earth) lead - see Section 1 of Chapter 5.

15 Unbolt the resonator support bracket from the engine compartment front crossmember, slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

16 Remove the screws securing the filter housing to the piping, unscrew the mounting bolt, then withdraw the housing (see illustration).

7.16 . . . undo screws УAФ to disconnect piping from housing, and
7.16 . . . undo screws УAФ to disconnect piping from housing, and mounting bolt УBФ to release housing

17 To dismantle the filter housing, undo the four screws and separate the top from the base of the housing; extract the foam filter, and clean it in a suitable solvent (see illustrations). If any of the housingТs components are worn or damaged, the assembly must be renewed.

7.17A Remove four screws to release filter housing top from base . . .
7.17A Remove four screws to release filter housing top from base . . .

7.17B . . .and withdraw foam filter for cleaning, if required - note valve in
7.17B . . .and withdraw foam filter for cleaning, if required - note valve in base of housing

18 Refitting is the reverse of the removal procedure.

Pulse-air piping
Note: This component, and those around it, will be very hot when the engine is running.

Always allow the engine to cool down fully before starting work, to prevent the possibility of burns.

19 Disconnect the battery negative (earth) lead - see Section 1 of Chapter 5.

20 Remove the air mass meter and resonator - refer to Chapter 4.

21 Unbolt the exhaust manifold heat shield; unclip the coolant hose to allow the upper part to be withdrawn. Apply penetrating oil to the EGR pipe sleeve nut, and to the pulse-air system sleeve nuts.

22 Remove the EGR pipe (see Section 6).

23 Remove the screws securing the filter housing to the piping - see illustration 7.16.

Unscrew the four sleeve nuts securing the pipes into the exhaust manifold, and remove the piping as an assembly, taking care not to distort it (see illustration).

7.23 Removing pulse-air piping - take care not to bend or distort it
7.23 Removing pulse-air piping - take care not to bend or distort it

24 Carefully clean the piping, particularly its threads and those of the manifold, removing all traces of corrosion, which might prevent them seating properly, causing air leaks when the engine is restarted.

25 On refitting, insert the piping carefully into the cylinder head ports, taking care not to bend or distort it. Apply anti-seize compound to the threads, and tighten the retaining sleeve nuts while holding each pipe firmly in its port; if a suitable spanner is available, tighten the sleeve nuts to the specified torque wrench setting.

26 The remainder of the refitting procedure is the reverse of removal.

Pulse-air filter housing and piping assembly
Note: These components, and those around them, will be very hot when the engine is running. Always allow the engine to cool down fully before starting work, to prevent the possibility of burns.

27 Disconnect the battery negative (earth) lead - see Chapter 5, Section 1. Unbolt the resonator support bracket from the engine compartment front crossmember. Slacken the two clamp screws securing the resonator to the air mass meter and plenum chamber hoses, then swing the resonator up clear of the thermostat housing (see Chapter 4).

28 Drain the cooling system (see Chapter 1) and disconnect the coolant hose and the coolant pipe/hose from the thermostat housing.

29 Unbolt the exhaust manifold heat shield.

Apply penetrating oil to the EGR pipe sleeve nut, and to the pulse-air system sleeve nuts.

30 Remove the EGR pipe (see Section 6).

31 Unscrew the filter housing mounting bolt.

Unscrew the four sleeve nuts securing the pipes into the exhaust manifold and remove the assembly, taking care not to distort it (see illustration).

7.31 Remove mounting bolt (arrowed) to remove complete pulse-air assembly -
7.31 Remove mounting bolt (arrowed) to remove complete pulse-air assembly - again, take care not to bend or distort piping

32 Clean the piping, particularly its threads and those of the manifold, removing all traces of corrosion, which might prevent them seating properly, causing air leaks when the engine is restarted.

33 On refitting, insert the piping carefully into the cylinder head ports, taking care not to bend or distort it. Apply anti-seize compound to the threads, and tighten the retaining sleeve nuts while holding each pipe firmly in its port; if a suitable spanner is available, tighten the sleeve nuts to the specified torque wrench setting.

34 The remainder of the refitting procedure is the reverse of removal. Refill the cooling system (see Chapter 1). Run the engine, check for exhaust leaks, and check the coolant level when it is fully warmed-up.


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