1995 RENAULT MEGANE SCENIC engine

ANTIPOLLUTION
Exhaust gas recirculation (EGR)
14
K7M engine
Mounting bolt for EGR solenoid valve 2.2
EGR solenoid valve bolt 1
Steel pipe bolts for EGR solenoid valve 1
TIGHTENING TORQUES (in daN.m)
REMOVING THE EGR SOLENOID VALVE
Remove the acoustic tie bar.
Disconnect:
- the air temperature sensor connector (1),
- the oil vapour rebreathing pipe (2).
Slacken the two clips (3) mounting the air duct (4)
and remove it.
Disconnect the accelerator cable (8).
99359R2
From the solenoid valve, disconnect:
- the vacuum pipe (5),
- the electrical connector (6).Remove the two mounting bolts for the EGR
solenoid valve, then remove the valve.
99358R1
REFITTING THE EGR SOLENOID VALVE
Renew the seal.
Refitting is then the reverse of removal.
SPECIAL NOTES
To remove the two steel pipes connecting the EGR
solenoid valve mounting to the exhaust manifold
and the inlet manifold, unclip the two clips (9) on
either side of each pipe.
14-14

ANTIPOLLUTION
Exhaust gas recirculation (EGR)
14
K7M engine
PURPOSE OF THE EGR SYSTEM
Recirculation of exhaust gas, or EGR, is used to
reduce the nitrous oxide (NOx) content of exhaust
gas.
The formation of nitrous oxide takes place at very
high temperatures in the engine combustion
chambers when driving under heavy loads.
By reducing the temperature of the combustion
chambers, the amount of nitrous oxide produced
is reduced. The simplest means of reducing the
combustion chamber temperature is to introduce
inert gas into the chamber.
Exhaust gas is made up of used inert gasses, so it is
recirculated into the inlet manifold in the correct
amount at the right time.
SOLENOID VALVE OPERATING PRINCIPLE
The EGR solenoid valve is operated by an RCO
signal from the injection computer. The RCO
signal modulates the opening in the solenoid
valve and this permits more or less exhaust gas to
be channelled to the inlet manifold.
Depending on this signal, the solenoid valve
applies to diaphragm (A) a quantified amount of
the manifold vacuum. Diaphragm (A) moves and
pulls valve (B) which permits the passage of
exhaust gas (by vacuum) to the inlet manifold.
DI1408-1
14-15

ANTIPOLLUTION
Exhaust gas recirculation (EGR)
14
K7M engine
OPERATING CONDITIONS FOR THE EGR SOLENOID
VALVE
The EGR system is operational if the following
conditions are met:
• coolant temperature greater than 20°C,
• air temperature greater than 5°C,
• no load position not recognised and throttle
position less than a set threshold, dependent
on engine speed (at 1024 rpm the throttle
position must be greater than 59 seen
using # 17 ;
at 5120 rpm the throttle position must be
greater than 103 seen using # 17),
• manifold vacuum greater than a certain
threshold.
The EGR solenoid valve is not operated if a fault is
detected with the :
- air temperature sensor,
- manifold pressure sensor,
- throttle potentiometer,
- EGR system.
A status bargraph on the XR25 visualises
operation of the EGR solenoid valve by the
computer.
It is however better to carry out a road test to
show this status. A test with the vehicle stationary,
engine operating under low loads is not
sufficient.
A faulty component in the EGR system will cause
an obvious worsening of the exhaust gas values.
CHECKING THE SEALING AND OPERATION OF THE
EGR SOLENOID VALVE
After the cooling fan has operated at least once,
stop the engine and turn the ignition off.
Disconnect the electrical connector.
Supply a 12 V feed directly to the solenoid valve.
Disconnect the pipe (D) connected to the vacuum
reservoir from the solenoid valve. In its place
connect a vacuum pump.
Create a vacuum of 300 mbars. The pressure
should not drop by more than 2 mbars per second
(120 mbars per minute).
Eliminate the vacuum to return the solenoid valve
to atmospheric pressure.
Run the engine at idle speed.
Create a vacuum of 300 mbars again, the engine
should run at idle speed, but unsteadily. If this is
not the case, replace the solenoid valve assembly.
Erase the computer memory after the operation.
14-16

99374R
ANTIPOLLUTION
Exhaust gas recirculation (EGR)
14
K7M engine
CLEANING THE EGR SOLENOID VALVE (if there is a
fault)
In certain cases, a deviation in the nitrous oxide
value at the exhaust may be noted due to the fact
that the EGR solenoid valve has become
contaminated. If this is noted, we recommend
that at approximately 50000 miles( 80 000 km),
the EGR solenoid valve is cleaned to ensure correct
depollution.
Remove as much contamination from the EGR
solenoid valve as possible then blow out with
compressed air.
Remove the two mounting bolts securing the
solenoid to the valve. Remove the solenoid
(ensure that no impurities enter the EGR valve
diaphragm area).
Remove all the pipes from the solenoid.
With no electrical feed, blow compressed air in
through union (C).
With 12 V feed, blow compressed air in through
union (B).This ensures that any possible impurities are
removed the way they entered the valve.
IMPORTANT: do not blow compressed air on the
EGR solenoid valve diaphragm.
Refit the pipes to the solenoid.
Renew:
- the O ring on union (C),
- the filter unit.
Refit the solenoid to the valve.
DI1409-1
14-17

ANTIPOLLUTION
Exhaust gas recirculation (EGR)
14
F8Q engine
Depollution for this engine uses recirculation to the inlet of some of the exhaust
gasses.
Recirculation of the exhaust gas reduces the combustion temperatures to reduce the
formation of nitrous oxides (NOx).
Recirculation is only permitted under certain load and temperature conditions.
99259R
1Inlet manifold
2Exhaust manifold
3EGR valve
4Air filter
5EGR solenoid
6Microswitch (on injection pump)
7Vacuum pump
8Injection pump load lever
9Brake servo
14-18

ANTIPOLLUTION
Catalytic converter
14
To meet the requirements of the EURO 96
standard, this vehicle is fitted with an oxidation
catalytic converter.
ROLE
The converter deals with the following three
pollutants at the same time:
- hydrocarbons (HC),
- carbon monoxide (CO),
- particulates, by a chemical oxidation reaction.
FUEL
No specific fuel is required for correct operation.
CONSTITUTION
The converter comprises:
- a monolith (1) in a honeycomb ceramic. A
substance containing precious metals is
deposited on the walls of the honeycomb
(mainly platinum),
- a metal jacket (2) retaining the monolith in its
shell,
- a shell (3) with inlet and outlet cones,
optimising the distribution of exhaust gas
flow.
99781R
CHECKING THE CATALYTIC CONVERTER
The performance of the catalytic converter on the
exhaust gas is difficult to check. The maximum
temperature of the exhaust gas from a diesel
engine is not sufficient to melt the monolith (in
comparison to petrol engines).
Diesel engine
14-19

ANTIPOLLUTION
Catalytic converter
14
FAULT FINDING
Faults which may cause a customer complaint due
to the catalytic converter.
1. Catalytic converter polluted by an
accumulation of soot, causing poor efficiency
of the converter.
Cause :
- prolonged town driving,
- air filter dirty,
- poor operation of the EGR system
- injection pump fault, etc.
Customer complaint:
- lack of power,
- large amount of smoke.
Solution:
De-contamination of the exhaust pipe by hard
driving on open roads.
2. Loss of efficiency due to premature aging of
the monolith*
Cause :
- injection incorrectly set,
- oil vapour rebreathing fault, etc.
Customer complaint:
Abnormal engine operation.
Solution:
Replace the catalytic converter.
(*) By prolonged operation at exhaust gas
temperatures which are too high (greater
than 800°C). Diesel engine
14-20

ANTIPOLLUTION
Catalytic converter - oxygen sensor
14
CHECKS TO BE MADE BEFORE THE ANTI-
POLLUTION TEST
Ensure:
- the ignition system is operating correctly
(correct spark plugs, correctly set plug gap,
high voltage leads in good condition and
correctly connected).
- the injection system is operating correctly
(supply is correct - check using the XR25).
- the exhaust pipe is correct and is sealed.
- the EGR is operating correctly.
Check the vehicle history if possible (run out of
fuel, lack of power, use of incorrect fuel).
CHECKING ANTI-POLLUTION STANDARDS
Run the engine until the engine cooling fan has
operated twice.
Connect a correctly calibrated four gas analyser to
the exhaust tail pipe.
Keep the engine speed at 2500 rpm for
approximately 30 seconds then let the engine
return to idle speed and note the pollutant values.
CO
≤0.3 %
CO
2≥14.5 %
HC
≤100 ppm
0,97
≤λ≤1.03
1
NOTE : λ = ————
richness
λ>1→lean mixture
λ<1→rich mixture
If, after these tests, the values are correct, the
antipollution system is correct.
If the values are not correct, additional tests must
be carried out:
- Check the condition of the engine (condition
of the oil, valve clearances, timing, etc,...),
- Check the correct operation of the oxygen
sensor (see section 17) ,
- test for the presence of lead (see following
page).
If the test for the presence of lead is positive, en-
sure the vehicle uses two or three full tanks of un-
leaded fuel before replacing the oxygen sensor.
If, after all these tests have been carried out, the
values still do not conform, the catalytic converter
must be replaced. Petrol engine
14-21