Idle-increase solenoid valve
Check
43 If this valve is thought to be faulty, unplug
its electrical connector and disconnect its
vacuum hoses, then connect a battery directly
across the valve’s terminals. Check that air
can flow through the valve’s passages when
the solenoid is energised, and that nothing
can pass when the solenoid is not energised.
Alternatively, connect an ohmmeter to
measure the resistance between the valve’s
terminals, and compare this reading to that
listed in the Specifications Section at the
beginning of this Chapter. Renew the valve if
it is faulty (see illustration).
44 The solenoid’s diode is fitted to control
any voltage “spikes” which might occur as the
solenoid is switched off. A faulty diode would
not, therefore, necessarily interfere with the
operation of the valve. If the diode is thought
to be faulty, however, it can be checked by
unplugging it and connecting an ohmmeter
across its terminals, to check that continuity
exists in one direction only. If continuity is
found in both directions, or in neither, the
diode is faulty, and must be renewed.
Renewal
45 If better access is required, remove the
plenum chamber (see Section 4).
46 Disconnect the battery negative (earth)
lead - see Section 1 of Chapter 5.
46 Unplug the valve’s electrical connector.
Unclip the valve from the bulkhead, then
disconnect its vacuum hoses and withdraw it.
47 Refitting is the reverse of the removal
procedure.
Warning: Inspection and repair of
exhaust system components
should be done only after enough
time has elapsed after driving the vehicle
to allow the system components to cool
completely. This applies particularly to the
catalytic converter, which runs at very
high temperatures. Also, when working
under the vehicle, make sure it is securely
supported on axle stands.
1 The exhaust system is composed of an
exhaust manifold, the front downpipe and
catalytic converter, and a rear section
incorporating two silencers (three on some
versions) and the tailpipe assembly. The
service replacement exhaust system consists
of three or four sections: the front
downpipe/catalytic converter, the
intermediate pipe and front silencer, and the
tailpipe and rear silencer. On some versions,
the tailpipe is in two pieces, with two rear
silencers. The system is suspended
throughout its entire length by rubber
mountings.
2 If any of these parts are damaged or
deteriorated, excessive noise and vibration
will occur.
3 Conduct regular inspections of the exhaust
system, to keep it safe and quiet. Look for any
damaged or bent parts, open seams, holes,
loose connections, excessive corrosion, or
other defects which could allow exhaust
fumes to enter the vehicle. Deteriorated
exhaust system components should not be
repaired - they should be replaced with new
parts.
4 If the exhaust system components are
extremely corroded or rusted together, they
will probably have to be cut from the exhaust
system. The most convenient way of
accomplishing this is to have a quick-fit
exhaust repair specialist remove the corroded
sections. If, however, you want to save money
by doing it yourself (and you don’t have an
oxy/acetylene welding outfit with a cutting
torch), simply cut off the old components with
a hacksaw. If you have compressed air,
special pneumatic cutting chisels can also be
used. If you do decide to tackle the job at
home, be sure to wear eye protection, to
protect your eyes from metal chips, and work
gloves, to protect your hands. If the
production-fit system is still fitted, it must be
cut at the points shown (see illustrations) for
the service-replacement system sections to fit.
5 Here are some simple guidelines to apply
when repairing the exhaust system:
Warning: The catalytic converter
operates at very high
temperatures, and takes a long
time to cool. Wait until it’s completely cool
before attempting to remove the
converter. Failure to do so could result in
serious burns.
(a) Work from the back to the front when
removing exhaust system components.
(b) Apply penetrating fluid to the exhaust
system component fasteners, to make
them easier to remove.
(c) Use new gaskets, rubber mountings and
clamps when installing exhaust system
components.
(d) Apply anti-seize compound to the threads
of all exhaust system fasteners during
reassembly.
(e) Note that the downpipe is secured to the
manifold by two bolts, with a coil spring,
spring seat and self-locking nut on each.
On refitting, tighten the nuts until they
stop on the bolt shoulders; the pressure
of the springs will then suffice to make a
leakproof joint (see illustration). Do not
overtighten the nuts to cure a leak - the
bolts will shear. Renew the gasket and the
springs if a leak is found (also see Chap-
ter 2, Part A).
(f)
Be sure to allow sufficient clearance
between newly-installed parts and all points
on the underbody, to avoid overheating the
floorpan, and possibly damaging the
interior carpet and insulation. Pay
particularly close attention to the catalytic
converter and its heat shield.
17 Exhaust system -
general information and
component renewal
4•12 Fuel and exhaust systems
17.4A Cutting point for renewal of production-fit exhaust system - 1.6 and 1.8 models
17.4B Cutting points for renewal of production-fit exhaust system - 2.0 models
17.5 Tighten exhaust system front
downpipe-to-manifold nuts as described -
do not overtighten them