Ford Fiesta (1989-1995). Instruction - part 36

Unplug the electrical connectors at the
camshaft position sensor and the coolant
temperature sensor, then unclip the wiring
from the ignition coil bracket, and secure it to
the manifold.
17 Remove the three screws securing the
wiring “rail” to the rear of the manifold.
Releasing its wire clip, unplug the large
electrical connector (next to the fuel pressure
regulator) to disconnect the wiring of the
manifold components from the engine wiring
loom.
18 Marking or labelling them as they are
unplugged, disconnect the vacuum hoses at
the manifold and throttle housing.
19 Undo the fuel feed and return lines
connecting the engine to the chassis. Plug or
cap all open fittings.

20 Unbolt the earth lead from the cylinder
head rear support plate/engine lifting eye,
then unscrew the bolt securing the support
plate/lifting eye.
21 Unscrew the nuts and bolts securing the
manifold to the cylinder head, and withdraw it.
Take care not to damage vulnerable
components as the manifold assembly is
manoeuvred out of the engine compartment.
22 With the manifold removed, clean all
traces of the old gasket from the mating
surfaces of the manifold and the cylinder head.

Refitting

All engines

23 Refitting is the reverse of the removal
procedure, noting the following points:

a) Fit a new gasket, then locate the manifold

on the head and install the nuts and bolts.

b) Tighten the nuts/bolts in three or four

equal steps to the specified torque,
working from the centre outwards, to
avoid warping the manifold.

c) Refit the remaining parts in the reverse

order of removal - tighten all fasteners to
the torque wrench settings specified
(where given).

d) Where drained, refill the cooling system

as described in Chapter 1.

e) Before starting the engine, check the

accelerator cable for correct adjustment
and the throttle linkage for smooth
operation (Section 5).

f) When the engine is fully warmed-up,

check for signs of fuel, inlet and/or
vacuum leaks.

4D•8 Fuel system - sequential electronic fuel injection engines

1595Ford Fiesta Remake

4E

1595Ford Fiesta Remake

Torque wrench settings

Nm

lbf ft

Pulse-air system piping sleeve nuts  . . . . . . . . . . . . . . . . . . . . . . . . . . . .

32

24

Exhaust manifold to cylinder head:

HCS engines  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

23

17

CVH engines (non turbocharged)  . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

12

CVH engines (turbocharged) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

28 to 31

21 to 23

PTE engines  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

12

Zetec engines  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

12

Chapter 4 Part E:
Exhaust and emission control systems

Catalytic converter - general information and precautions  . . . . . . . .

4

Emission control system check . . . . . . . . . . . . . . . . . . . .See Chapter 1
Evaporative emissions control system - checking and component

renewal  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6

Exhaust manifold - removal and refitting  . . . . . . . . . . . . . . . . . . . . .

3

Exhaust system - renewal  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Exhaust system check . . . . . . . . . . . . . . . . . . . . . . . . . . .See Chapter 1
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Positive crankcase ventilation system - checking and component

renewal  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

Pulse-air system - checking and component renewal  . . . . . . . . . . .

7

Underbonnet check for fluid leaks and hose condition . .See Chapter 1

4E•1

Specifications

Contents

Easy, suitable for
novice with little
experience

Fairly easy, suitable
for beginner with
some experience

Fairly difficult,
suitable for competent
DIY mechanic

Difficult, suitable for
experienced  DIY
mechanic

Very difficult,
suitable for expert DIY
or  professional

Degrees of difficulty

5

4

3

2

1

1

General information

Exhaust system

The exhaust system is composed of an

exhaust manifold, the front downpipe and
catalytic converter (where fitted), and a main
section incorporating two silencers. The
service replacement exhaust system consists
of three sections: the front downpipe/catalytic
converter, the intermediate pipe and front
silencer, and the tailpipe and rear silencer.
The system is suspended throughout its entire
length by rubber mountings.

Emission control systems

To minimise pollution of the atmosphere

from incompletely-burned and evaporating
gases, and to maintain good driveability and

fuel economy, a number of emissions control
systems are used on these vehicles. They
include the following:

a) The engine management system

(comprising both fuel and ignition sub-
systems) itself.

b) Positive Crankcase Ventilation (PCV)

system.

c) Evaporative emissions control (EVAP)

system.

d) Pulse-air (PAIR) system.
e) Catalytic converter.

The operation of the systems is described

in the following paragraphs.

Positive crankcase ventilation system

The function of the crankcase ventilation

system is to reduce the emissions of
unburned hydrocarbons from the crankcase,
and to minimise the formation of oil sludge. By
ensuring that a depression is created in the
crankcase under most operating conditions,
particularly at idle, and by positively inducing

fresh air into the system, the oil vapours and
“blow-by” gases collected in the crankcase
are drawn from the crankcase, through the air
cleaner or oil separator, into the inlet tract, to
be burned by the engine during normal
combustion.

On HCS engines, the system consists of a

vented oil filler cap (with an integral mesh
filter) and a hose connecting it to a connector
on the underside of the air cleaner housing. A
further hose leads from the adapter/filter to
the inlet manifold. Under conditions of idle
and part-load, the emissions gases are
directed into the inlet manifold, and dispensed
with in the combustion process. Additional air
is supplied through two small orifices next to
the mushroom valve in the air cleaner
housing, the object of which is to prevent high
vacuum build-up. Under full-load conditions,
when the inlet manifold vacuum is weak, the
mushroom valve opens, and the emissions
are directed through the air cleaner housing

into the engine induction system and thence
into the combustion chambers. This
arrangement eliminates any fuel mixture
control problems. The operating principles for
the system used on the Endura-E engine are
basically the same as just described with
revisions to the component locations and
hose arrangement.

On CVH and PTE engines, a closed-circuit

type crankcase ventilation system is used, the
function of which is basically the same as that
described for the HCS engine type, but the
breather hose connects directly to the rocker
cover. The oil filler cap incorporates a
separate filter in certain applications.

On Zetec engines, the crankcase ventilation

system main components are the oil
separator mounted on the front (radiator) side
of the cylinder block/crankcase, and the
Positive Crankcase Ventilation (PCV) valve set
in a rubber grommet in the separator’s left-
hand upper end. The associated pipework
consists of a crankcase breather pipe and two
flexible hoses connecting the PCV valve to a
union on the left-hand end of the inlet
manifold, and a crankcase breather hose
connecting the cylinder head cover to the air
cleaner assembly. A small foam filter in the air
cleaner prevents dirt from being drawn
directly into the engine.

Evaporative emissions control system

This system is fitted to minimise the escape

of unburned hydrocarbons into the
atmosphere. Fuel evaporative emissions
control systems are limited on vehicles
meeting earlier emissions regulations;
carburettor float chambers are vented
internally, whilst fuel tanks vent to atmosphere
through a combined roll-over/anti-trickle-fill
valve. On vehicles meeting the more stringent
emissions regulations, the fuel tank filler cap
is sealed, and a charcoal canister is used to
collect and store petrol vapours generated in
the tank when the vehicle is parked. When the
engine is running, the vapours are cleared
from the canister (under the control of the
EEC IV engine management module via the
canister-purge solenoid valve) into the inlet
tract, to be burned by the engine during
normal combustion.

To ensure that the engine runs correctly

when it is cold and/or idling, and to protect
the catalytic converter from the effects of an
over-rich mixture, the canister-purge solenoid
valve is not opened by the EEC IV module
until the engine is fully warmed-up and
running under part-load; the solenoid valve is
then switched on and off, to allow the stored
vapour to pass into the inlet tract.

Pulse-air system

This system consists of the pulse-air

solenoid valve, the pulse-air valve itself, the
delivery tubing, a pulse-air filter, and on some
models, a check valve. The system 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.

The system’s primary function is raise

exhaust gas temperatures on start-up, thus
reducing the amount of time taken for the
catalytic converter to reach operating
temperature. Until this happens, the system
reduces emissions 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.

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 EEC IV module,
so that it only functions during engine warm-
up, when the oxygen sensor is not influencing
the fuel/air mixture ratio.

Catalytic converter

Catalytic converters have been introduced

progressively on all models in the range, to
meet the various emissions regulations.

The catalytic converter is located in the

exhaust system, and operates in conjunction
with an exhaust gas oxygen sensor to reduce
exhaust gas emissions. The catalytic
converter uses precious metals (platinum and
palladium or rhodium) as catalysts to speed
up the reaction between the pollutants and
the oxygen in the vehicle’s exhaust gases, CO
and HC being oxidised to form H

2

O and CO

2

and (in the three-way type of catalytic
converter) NO

x

being reduced to N

2

. Note:

The catalytic converter is not a filter in the
physical sense; its function is to promote a
chemical reaction, but it is not itself affected
by that reaction.

The converter consists of an element (or

“substrate”) of ceramic honeycomb, coated
with a combination of precious metals in such
a way as to produce a vast surface area over
which the exhaust gases must flow; the whole
being mounted in a stainless-steel box. A
simple “oxidation” (or “two-way”) catalytic
converter can deal with CO and HC only,
while a “reduction” (or “three-way”) catalytic
converter can deal with CO, HC and NO

x

.

Three-way catalytic converters are further
sub-divided into “open-loop” (or
“unregulated”) converters, which can remove
50 to 70% of pollutants and “closed-loop”
(also known as “controlled” or “regulated”)
converters, which can remove over 90% of
pollutants.

In order for a closed-loop catalytic

converter to operate effectively, the air/fuel
mixture must be very accurately controlled,
and this is achieved by measuring the oxygen
content of the exhaust gas. The oxygen
sensor transmits information on the exhaust
gas oxygen content to the EEC IV engine

management module, which adjusts the
air/fuel mixture strength accordingly.

The sensor has a built-in heating element

which is controlled by the EEC IV module, in
order to bring the sensor’s tip to an efficient
operating temperature as rapidly as possible.
The sensor’s tip is sensitive to oxygen, and
sends the module a varying voltage
depending on the amount of oxygen in the
exhaust gases; if the inlet air/fuel mixture is
too rich, the sensor sends a high-voltage
signal. The voltage falls as the mixture
weakens. Peak conversion efficiency of all
major pollutants occurs if the inlet air/fuel
mixture is maintained at the chemically-
correct ratio for the complete combustion of
petrol - 14.7 parts (by weight) of air to 1 part
of fuel (the “stoichiometric” ratio). The sensor
output voltage alters in a large step at this
point, the module using the signal change as
a reference point, and correcting the inlet
air/fuel mixture accordingly by altering the fuel
injector pulse width (injector opening time).

Removal and refitting procedures for 

the oxygen sensor are given in Parts B, C 
and D of this Chapter according to fuel
system type.

2

Exhaust system - renewal

2

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.

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. Alternatively, you can simply cut off
the old components with a hacksaw. 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 for the service-
replacement system sections to fit. The best
way of determining the correct cutting point is
to obtain the new centre or rear section first
then, with the old system removed, lay the
two side by side on the ground. It should now
be relatively easy to determine where the old
system needs to be cut, and it can be marked
accordingly. Remember to allow for the
overlap where the two sections will plug
together.

4E•2 Exhaust and emission control systems

1595Ford Fiesta Remake

Here are some simple guidelines to apply

when repairing the exhaust system:

a) Work from the back to the front when

removing exhaust system components
(see illustration).

b) Apply penetrating fluid to the exhaust

system component fasteners, to make
them easier to remove.

c) Use new gaskets, rubber mountings and

clamps.

d) Apply anti-seize compound to the threads

of all exhaust system fasteners 

e) Note that on some models, 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 gastight joint. Do
not overtighten the nuts to cure a leak -
the bolts will shear. Renew the gasket and
the springs if a leak is found (see
illustrations).

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.

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.

3

Exhaust manifold -
removal and refitting

3

Removal

Note:  Never work on or near the exhaust
system and in particular, the catalytic
converter (where fitted), while it is still hot. If
this is unavoidable, wear thick gloves, and
protect yourself from burns should you
accidentally touch a hot exhaust component.

All engines except Zetec

Note: On turbocharged engines, removal and
refitting procedures for the exhaust manifold,
complete with turbocharger are given in 
Part C, Section 20.
1 Disconnect the battery negative (earth) lead
- see Chapter 5A, Section 1.

Exhaust and emission control systems  4E•3

2.2b  Exhaust system downpipe-to-

manifold securing nuts (arrowed)

2.2a  Typical exhaust system and heat shield arrangement 

(1.4 litre CVH CFi model shown)

2.2e  Release the spring clip to extract the

securing bolt from the manifold, when

required

2.2d  Renew the exhaust system

downpipe-to-manifold gasket to prevent

leaks

2.2c  Showing securing bolts - note coil

spring, and shoulder on bolt

4E

1595Ford Fiesta Remake