TTEC4843 :- FUELS AND FUELS SYSTEM

Date:-19/9/2011

IDLE SPEED DEVICE:
In this task we tested the idle speed device.

• First thing was asked to check which type of cold or fast idle speed control does our vehicle use?- our was "stepper motor".
• And the base idle speed is adjusted here by ECU. 
• Here the cold / fast idle speed is control activated by "ECU".
• The correct procedure for checking this control is- ,firstly check the resistance winding test, then test duty cycle and frequency (spec 9-14v) and connect the bridging wire on terminal TE1 and E1 to check control.
• our result for the resistance in winding: used multimeter n used to find btw two pins.
  RSO-EO1=33 OHMS
  RSC-EO1=24 OHMS
• Then we used the digital meter to measure the duty cycle and frequency that operates the IACV- OUR RESULT WAS ... !DUTY:-Open 51% & close 49% 
  Frequency:- 244(open) & 244 (close) hz

Report: Our engine was in all good condition , the ECU adjust the base ideal speed where as idle speed control is determined by engine temperature and the time engine is cold means more air flow. Then we checked the continuity, we measured the resistance windings by keeping the black & red probe on RSO (open) & RSC (close)..which was 33 ohms and 24 ohms. Then had our duty test which was 51% & frequency came to be 244hz , that showed us how many times it turns on/off.

Checking Fuel Lines:

Firstly we checked the condition of fuel hoses, :- firstly had a visual check on the fuels lines on the vehicle, then checked for any cracks or perished rubber hoses, are the lines tight,check for any leaks ,check if its lose or bend.

RESULT:- PASS,.... OUR VISUAL CHECK ON FUEL HOSES IS ALL GOOD , THERE IS NO LEAKS AND EVERYTHING IS TIGHT & GOOD CONDITION.

CHECKING FUEL PUMP(fuel injection high pressure):

It is an electrical pump which can be mounted either inside or outside the fuel tank.

Here we learned how to work with the high pressure fuel. Firstly we use manual book to follow the procedure..as follow.

• we check the running pressure at idle.
• we also check the running pressure under full engine load.
• Then check the maximum output pressure of the fuel pump
• And in last check the residual line pressure.

SAFETY PRECAUTION TO BE OBSERVED: Check for the rsidual pressure when car is off, decrease the pressure by disconnecting the fuel relay,while the car is on.

MANUFACTURER'S SPECIFICATION: 

Ignition on: 265-305kpa

jumper disconnected: 206-255kpa

ignition off:147kpa

OUR TEST RESULT:

Pressure at idle:270kpa

WOT pressure:340kpa

Max Pressure:560kpa

Residual Pressure:255kpa

All, good the pressure were within specification.So, all good.

CHECKING FUEL PUMP FLOW:
After the pressure checks ,we can check the fuel flow through the system. Firstly after droping the residual line pressure, remove the pressure gauge from the fuel system. Then with the help of the manufacturer we'll check the fuel flow *after the pressure regulator for normal pump & *before the regulator for maximum pump flow.


Then ,it shows us the flow rate in minute for the pressure regulator for the fuel pump.

MANUFACTURER'S SPEC: 195-MAX FLOW & 135-NORMAL FLOW

OUR TEST RESULT:
                                                                              NORMAL
10SEC-540ML(.54L)                                        10SEC- .39L
60SEC-3240ML(3.24L)                                      60SEC- 2.34L
1HOUR-194400ML(194.4L)                               1HOUR- 140.4L

LOCATE AND IDENTIFY SELF TEST CODES AND ISOLATE CAUSE.

In this we learned how to identify and do self test code.
The vehicle we started with was Toyota 4AFE , flashing light on the dash board is the method used to display the diagnostic codes.

SPECIAL TOOLS AND EQUIPMENTS WE USED : jumper wire , scan tools to check the faulty codes and scope to check wave pattern.

*Firstly we bridge the wire from TE1 TO E1 terminals and then count the number of blinks of engine light on the car dash board.

The fault detected from us was 22,31,24
22- water temp.circuit (coolant sensor)
31-vacuum sensor circuit(MAP).
24-Intake air temp.sensor.

*THEN ,we rectified the faults , firstly we checked the connection on sensors.

• MAP sensor- were checked using vacuum pump and voltage regulator
• Coolant sensor temp.switch- checked by using heat gun water and thermometer.
• Air temp.sensor - heat with heat gun & check temp.with leaser sensor.

FINALLY:
The faults were solved with d help of the blinking light we recognized the above codes...and started finding the problem.in there , All the above codes were solved by reconnecting the circuits or wire, which were unplugged, And during in between the lights use to confuse us by blinking differently ,for this after every fault solved we should take the key off and start after little while.

SERVICE AN AIR CLEANER:
 It is really important that the air filter should be clean and working properly .It is not filtering the air entering  the engine dirt and particles as it will cause damage to the engine, and if itz blocked then it gonna affect the emission and fuel consumption.
Firstly we removed the air filter and and checked for damage or excessive dirt or any oil contamination to the filter element.
*all was good,it passed the inspection
*condition still all good and can run till the next service without any problem.

PCV VALVE:
we performed on the testing of pcv valve, first thing we did  was ,we clamp the rubber hose(using a brake hose clamp) going to the pcv valve does the idle change?YES(SO,PASSED)

*Then we checked for clicking sound which can be checked by listening,so as to knew that the plunger can move freely? yes

AS DURING CLAMPING THE RUBBER HOSE THERE WAS AN IDLE  SOUND CHANGE , WHICH SHOWS PCV IS IN GOOD CONDITION. SO, NO FAULTS AND ALSO THERE WAS CLICKING SOUND WHICH MEANT THE PLUNGER IS MOVING FREELY.
ALL GOOD.


VACUUM OPERATED EGR VALVE:
Today we tested vacuum operated EGR valve.


Record the EGR test result:

• Did the engine idle smoothly at normal operating temperature?-YES
• Did the idle speed change with vacuum applied to the EGR valve? -YES
• Did the valve show any signs of air leaks through the stem seal? -NO
• Is the EGR system working to specification? -YES

OUR RESULT:
No service require yet, all working good as manifold doesn't suck gases on idle and an crusing gases started being vacuum into NOX area in manifold.

The EGR is used to control/reduce NOX emission by introducing exhaust gas back into inlet ,there by reducing the combustion temperature.

ADJUSTMENTS AND EMISSIONS:
 In this we learned about adjustments and emission, firstly we tested a vehicle with carburetor and without a catalyic converter and then recorded the result.

• Firstly we bring the engine to operating temperature.
• Then we prepared the infra-red gas analyzer as required.
• Then calibrate the gas analyzer gauges.
• After which we set it to zero and adjust the span settings (analogue gauges).
• Fitted the sampler hose into the exhaust of the vehicle.
• In last we took the exhaust gas sample.

 And our result was:


ACTUAL BEFORE ADJUSTMENT                                   INDUSTRY STANDARD
H.C. - 159 ppm                                                                       H.C.  - 50 to 500 ppm
C.O. -0.528 %                                                                         C.O. - 0.5 to 1.5 %
CO2 - 14.24 %                                                                         CO2 - 13 TO 14.5 %
O2 - 0.18%                                                                               O2 - 0to 2.0 %


RESULT : YES, all good reading within specification.


EFI VEHICLE TEST:


ACTUAL                                                 INDUSTRY STANDARD

H.C. - 178 ppm                                           H.C.  - 50 to 500 ppm
C.O. -0.824 %                                           C.O. - 0.5 to 1.5 %
CO2 - 13.84 %                                          CO2 - 13 TO 14.5 %
O2 - 1.14%                                                  O2 - 0to 2.0 %


*THE RESULT WAS ALL GOOD.
The difference we noticed in two sets of reading as follow:

• HC it alwayz should be lower , as if its high then the specification it refer that the fuel is not buring properly.
• CO  is also same as HC , they may  too cause rich mix 
• if CO2 is high , it means engine burns efficiently , however if O2 is high , it means the mix is  too lean and its not good.

REMOVAL & REPLACEMENT OF DIESEL FUEL INJECTORS:

We learned how to check diesel injectors and inspect.

we firstly removed the diesel fuel injectors, then using harbridge test master machine we tested each injector.Then putting each injector one by one on the machine check for the spray pattern.And if there is any problems with them we set our machine to 18 psi, then pumped the injectors and we could not meet the specification as the spec fr ATM WAS 118 to 125 bt the result was all out. So need to change all four injector as they couldnt meet the specification n have not gud spray pattern evn thr was leakage.

BLEED AIR FROM A DIESEL INJECTION SYSTEM:-

HERE WE LEARN HOW TO BLEED THE AIR FROM DIESEL INJECTION SYSTEM.Remove the fuel pump filter to bleed from the hand , then loose the fuel line and disconnect it from the fuel distributor, then put the fuel filter back and start pumping the filter from this the fuel will start comiing out from fuel line , first it will not be soo flued because of air pressure bubles inside but once it get fluent, put the fuel line back .start the engine and checked., all good.

Decribe the location of the air bleed screw on d engine??

ANS- it was on the fuel pump top close to the fuel return.

TESTING ELECTRONIC SHUT OFF VALVE:-
 

We tested the electronic shut off valve with the ignition on, then we have to use the multimeter to test the voltage coming from ignition switch to the electronic shut off solenoid.

voltage- 12.4 v

Resistance of solenoid winding- 9.5 ohms

 OPERATION O SOLENOID:

Solenoid is not NA, but we checked the one which is attached on the engine diesel pump. So, when we connect the wire of solenoid then the clicking sound indicates the solenoid working properly And our result 12.4v shows that the solenoid is working as voltage is detected & the resistance confirms us the coil is working properly.

DIESEL INJECTOR PUMP TIMING:

HERE WE LEARNED HOW TO TIME A DIESEL INJECTOR PUMP.

DTI-Remove the cam belt and rotate the pulleys to TDC and reset them to there points , put the belt back and tight the pulleys back & tight the belt , taking care to have the timing makes aligner and  engine on TDC firing number one.
SPILL TIMING- done all good, jst have to remove the full injector lines , and adjust it.

Special tools- DTI gauge, socket tools , allen key /hen key tools.

TESTING GLOW PLUGS:

We tested the glow plugs.

                    glow plug1        glow plug2         glow plug 3         glow plug4

current draw         8amps                    8amps                    8amps                       8amps


colour of glow        turns red                  turns red               turns red                 turns red

plug tip. 

RESULT: Firstly we removed the 4 glow plugs and earth them to the ground to check weather they are working or not , we checked 4 of them all were pass as the top of them turns to be red.As they turn red that means there are working properly and there wont be any trouble.this shows us that the plugs are useable and cn be charged.

TTEC4843 :- FUELS AND FUELS SYSTEM

                TTEC4843:- EFI OFF CAR

CLEANING INJECTORS:-
In this we learned how to check and clean electronic fuel injectors.

• Their were 4 injectors .
• Then we listened each injector with stethoscope while the engine is running..all were audible,so all good.
  • • • • • • • • • • • • • • • • • 
                                    

*Then we expose the wiring into the back of the injector plug, we take one injector at a time  and connect an LED checker ,then record if the light flashes.

• All 4 LED indicates the pulse present.

*Now, checked the injector operation by the engine speed.

•  yes , there was a 1000rpm drop during a single disconnect of injector.

*Also checked the resistence of each injector winding with the ignition off.

• all 4 winding resistance was 15.4 ohms. 
• So all good as under specification ( 12-16ohm)

*off car injector testing

• we performed it on all the 4 injectors we fitted them into the testing machine and checked for the injectors.
• check if  all fitting are secure before mounting them in the test machine.

*specification:-

• injector leakage:- 1drip per minute.
• injector flow rate 220cc per minute flow rate at 3.0 hz.

All 4 injector need intention=spray pattern flow rate not good fr all 4 injectors and where as injector leakage was also there.
*clean them or replace.

Important Note: 

• when replacing fuel injector do not forget to, replace all top "o" rings and lower "o" rings.
• Ensure injector seals and "o" rings are lubricated and injectors correctly located.
• And all fuels lines and connections  are correctly located without leaks.
  

AIR FLOW METER RESISTANCE TEST - FUEL INJECTION DIAGNOSIS:-

In todays task we checked the resistance on the air flow meter using ohms meter by checking the potentiometer circuits and determine the air flow sensor condition by comparing the result with the manufacturing specification.

• first thing we did was tested E1-FC closed had reading of infinty
• E1-FC open  0.2ohms

And it shows if the fuel pump relay is effected on pump operation with high resistance across the two terminals, this will not give right measurement and amount of fuel.
*As higher is the resistance so lower will be the voltage and fuel pump relay wont get enough current to open the fuel pump.

*AALL OTHER SENSORS HAS BEEN DISCUSED IN REPORT

AIR FLOW/MASS SENSOR TESTING:

• we started by looking for the air flow sensor on the outside of air cleaner.
• it is bolted to the air cleaner with the ducting connected to the throttle body.
• it could be in following shape:L type moving vane,hot wire ,sliding piston(mazda,ford), Karman voltex air pulse (mitsubishi) etc.

*the one we detected was L type moving vane.

*we need to have multikmeter ,heat gun and heat reader laser gun.

Acc. to the stated procedure the sensor could not meets the specification and can not be repaired

AIR TEMPERATURE SENSOR:We tested the air temperature sensor and using multimeter check sensor resistance.

Terminal no.             Tempersture               Reading                      Specification  
E2-THA                       20*C                           2130                            2000-3000 ohm
                                     60*C                           120                                 400-700  ohm






THROTTLE POSITION SENSOR (LINEAR TYPE): LINEAR TYPE IS THE ONE WHICH SENDS READING EVEN WHEN THE BUTTERFLY IS MOVING FROM  CLOSE TO OPEN OR OPEN TO CLOSE

• We check that the throttle leakage move smoothly.
• Check for the vaccum with your fingers at N port while engine start.
•  inspect throttle position sensor.
• inspect throttle body,throttle body valve and clean throttle body.

When we inspected the throttle position sensor, firstly discoonect the sensor, insert the feeler gauge   between the throttle stop screw and stop lever and ohm meter measure the resistance between each terminal.



multimeter:positive:-voltage in  ,                         negative:- fully throttle

TB fully open = 0V

TB closed =infinity

Now multimeter 

positive or red lead=Voltage in.        black lead or negative = on idle position 

TB fully closed =0V

TB open =infinity

THROTTLE BODY CLEANING:

Throttle body gets dirty from engine gas recirculation

(EGR), there is a small hose that spends post combustion gases into the intake.The post combustion gas dirties the throttle body and rest of the intake manifold,so when we clean throttle body oil  and dirt then it promotes engine effeciency.

TYPES OF AIR MASS SENSOR:

• L jetronic type air flow sensor.
• LH jetronic hot wire type sensor .
• D jetronic manifold absolute pressure sensor.
• karman vortex air flow sensor.  

TTEC4843 :- FUELS AND FUELS SYSTEM

TTEC4843:- LAMBDA TEST 

TTEC4843 :- FUELS AND FUELS SYSTEM -PRACTICAL

Date:- 13/9/2011

In lambda test we ,learned to make the lambda tester. Which helps us to determine ,in a real time , if the air fuel ratio of combustion engine is rich or lean.

*Equipment used to make the tester :- Rectifier diodes, zener diodes , capacitors , 3 LEDS (GREEN,YELLOW,RED) , Jumper wires, and (RED, BLACK, GREEN) IC CHIP LM324.









*FIRSTLY WE HAVE TO TAKE A O2 SENSOR PCB BOARD ,AND INSTALL THE ALL ABOVE EQUIPMENT'S TO IT.


*THEN STEP BY STEP WE STARTING SOLDERING THE ABOVE EQUIPMENT'S ON THE PCB BOARD.

RESULT:-It shows us the working of the lambda tester in following way:

• shows us the rich & lean mixture with the help of LED's
• when it turns red it means, the mixture is rich.
• while the YELLOW LED is the signal going between the RED LED and the GREEN LED, where as the GREEN LED shows us the car is running on lean and is normal.

TTEC4843 :- FUELS AND FUELS SYSTEM

TTEC4843: Ignition Off CAR & ON CAR



>In this we started with testing distributor components for serviceability.

Here we obtain and test 3 vacuum advance units for serviceability.

• We will use Mini -Vac name tester. 
• And before carrying out serviceability tests on the vacuum operated components- we should release the excess pressure by the valve in mini vac.

our vacuum unit test result:

1. mm/hg (mercury) held:- 65
   
   Did the diaphragm linkage move:-yes
   Did the diaphragm hold vacuum:- yes
   So, doesn't need any service, vacuum is in good condition.
2. mm/hg (mercury) held:- 71
   
   Did the diaphragm linkage move:-yes
   Did the diaphragm hold vacuum:- yes
   So, doesn't need any service, vacuum is in good condition.
3. mm/hg (mercury) held:- 69
   
   Did the diaphragm linkage move:-yes
   Did the diaphragm hold vacuum:- yes
   So, doesn't need any service, vacuum is in good condition.

Now we have to test the ignition coils:

• Firstly we have to obtain the 2 coils with different part numbers nos.
• Then list all coils part numb, voltage, internal resistance specification as per specification manual.

coil specification:

• coil 1 no: C6R-500
  coil 1 voltage: 12V
  coil 1 primary: 3.4
  coil 1 secondary: 7.84 kohm
• coil 2 no: C1T-118
  coil 2 voltage: 12V
  coil 2 primary: 3.5
  coil 2 secondary: 9.2 kohm

REMEMBER:
Always check the meter error and deduct that value off your final reading.
>.5ohm(our value result)


(most important when using the 0-200 ohm scale)The test result after deducting the error from the above result.
coil 1 primary: 2.9
coil 1Secondary: 7.34
coil 2 primary: 3
coil 2 Secondary:  8.7

*>That showed us our primary is in good condition and has reached itz spec which is 2-8.*>For secondary itz fail as it couldnt reach itz specification which is 18 kohms.

so , as a result change d coils if the result out of spec. n that means d coils r need to be replaced.


Now we have to test the ballast resistors:

1. obtain 2 ballast resistor with different part numbers.
2. list part numbers and resistance specification.
3. Then have to measure the resistance of resistors.

SPECIFICATION:

*Ballast resitor 1No: 2.0ohm.               *Ballast resistor no.2: 2.3ohm
*Ballast resistor no.1 ohm spec. : 1.6ohm. *Ballast resistor no.2 ohm spec:1.6ohm.

MEASURED RESISTANCE VALUES:

Ballast resistor no.1 measured ohms:- 1.6 > pass
Ballast resistor no.2 measured ohms:-1.9 > fail 

we check the ballast resistor with the multimeter setting it on 200 ohms that showed us that one is in good condition and other one is fail, not in specification.

Then we moved on by Testing stall current and voltage drop.

1. Firstly wire up the ballast resistor in series with two individual coils that have different primary winding valve. (U NEED TWO MULTIMETERS FOR THIS)
2. insert amp meter in series and note the current flow valve.
3. And then measure the note the voltage drop across the ballast resistor and coil primary.

 COIL 1 NO:  Su 12RCOIL 1 VOLTAGE DROP : 6.0 v

BALLAST RESISTOR VOLTAGE DROP: 5.7v
COIL1 PRIMARY CURRENT VALUE: 4.20 amp

COIL 2 NO: C6R-500
COIL 2 VOLTAGE DROP: 0.3V
COIL 2 PRIMARY CURRENT VALUE: 10 AMP

This shows us the result that the testing stall current value and voltage drop is good and we had good reading as we spose too, that showed us coils and ballast resistor...r in good condition for one n not for other.



THE NEXT TASK WAS TO STATICALLY TIMING AN ENGINE: 

                                                                                                          

1. Firstly we removed the distributor cap and high tension leads from the engine.
2. Then remove the sparks plugs from the cylinder head.
3. remove the distributor (disconnect the low tension cable connection)
4. remove the tapped cover assembly.
5. remove ignition key from ignition switch , for your safety

THEN WE ADJUSTED THE CRANKSHAFT ON .5 BEFORE TOP DEAD CENTER. SO AS TO SET CORRECT ENGINE ROTATION.

Abhinav ttec4843 report

                             REPORT; inputs ,outputs ,closed loop

• MAP: The Map sensor (Manifold absolute pressure sensor works as a input) is one of the senor used in an internal combustion engine's electronic control system. The engine which uses  map sensor are typically fuel injected. The map sensor provide instantaneous manifold pressure to engine's ECU. The data by ECU is used to calculate air density and determine engine air mass flow, which sends signal to ecu to rich or lean d flow of fuel if needed, or can have less air in the manifold.
  And the relationship between the map sensor and iac is idle air control is that the map sensor determine the air flow and telll ecu and iac determine how much air should be put in air fuel mixture,fuel injector stays open longer if more air is detected.
  
• MAF: MAF sensors (stands for MASS AIR FLOW ) and is to find out the mass of air entering a fuel injected internal combustion engine. The air mass is necessary information which is provided to ECU to balance and deliver the correct fuel mass to engine.Air changes its density as it expands and contacts with temperature and pressure.
  There are two common types of mass air flow sensor 1.Vane meter sensor and 2.hot wire sensor.
  
  
• CKP: A crankshaft sensor is an electronic device used in an internal combustion engine to monitor the position or rotational speed of the crankshaft. This information is used by engine management system to control ignition systems to control ignition system timings and other engine parameters. The crank sensor can be used in combustion with a similar camshaft position sensor to monitor the relationship between the pistons and valves  in the engine, which is particularly important in engine with variable valve timing.so this method is use to 'syncronise'  a four stroke engine upon starting, allowing the management system to know when to inject the fuel.
  Relationship btw input&output:injector,fuel pump relay,pcv.
  
• TPS: A TPS (throttle position sensor)  is used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located at the butterfly spindle so that it can directly monitor the position of the throttle valve butterfly, sensor is  usually potentiometer and depending upon the position it provides the resistance. The sensor signal is used by the ECU as an input to control itz system.the ignition timing and  fuel injection timing are altered depending upon the position of the throttle and also depending upon rate of change of that position.
  Relationship btw input&output: injectors, auxiliary air valve.
  
• CMP: A CMP (stands for camshaft position sensor) sensor provides the camshaft position information to ecu, the cam sensor tells the computer where your cam is in its rotation. The info is used to determine spark timing and fuel delivery and which is used by the powertrain control module for fuel synchronization.
  Relationship btw input&output: injectors , EST.
  
• ECT: An ECT (stands for engine coolant temperature) sensor is a sensor that is screwed into the engine block or cylinder head and is used to determine the temperature of the engine coolant, and the ect sensor is basically a thermistor that changes resistance with temperature . when the ect is high (hotter), the resistance is low and when ect is low(cooler) the resistance is high. The resistance reading is sent to the vechicals pcm/ecm  9 cars on board computer) and can be used to activate emmision control or turn the engine cooling fan on.
  
• O2 SENSOR: The o2 sensor is installed to the exhaust manifold to monitor the excess or free , o2 in the exhaust gases. The O2 sensor contains a zirconia element  which at temperature above 360 degree C produces voltages that depends on the O2 contact with the sensor element compared to the O2 present atmosphere , the outside of O2 sensor has a small vent hole ( beneath the external metal cover of the sensor). so sends the signal to the ecu of amount of O2 gases after the fuel combustion, n which identify  the amount of O2 then ecu decided more or less fuel should be injected,higher voltage means low O2 means running rich  and lower voltage means higher O2 which mean is lean.
  Relationship btw input&output: injectors , EGR.
ACTUATORS:

• INJECTORS:It is electronic controlled valve. It is supplied with pressurized fuel by the fuel pump in your car and it is capable of opening and closing many times per second. they inject fuel into the combustion chamber when the valve opens on the  intake stroke. The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. and fuel rail supplies the pressurised fuel to all the injectors.
  
• EGR:  It stands for Exhaust gas Recirculation and open when there is back pressure from the exhaust and recirculate the gas back to combustion chamber.It redirect the gas when it sensez the engine is warm and prevent overheating. warm up the car fast when car is first started.
  
• EST:  It control the combustion timing ,Takes measurements in voltage, It modifies the sparks advance when detonation occur and  also trigger when the distributor works.
  
• FUEL PUMP RELAY:  When the coil is energized you can generally quietly hear the fuel pump buzzing for a few seconds.,Then the fuel pump will come on before the engine has a chance to start up so that the fuel system will be pre pressurized , If the relay has gone bad the fuel pump will never come on and test the continuity with ohm meter when energized.
  
  
• AUXILIARY AIR VALVE:  When car is idle it provide air for the fuel to mix with , is measured in hertz and duty cycle and if this does not work the engine will start running too rich and cut off.
  
  CLOSED LOOP OPERATION:-in this mode of operation the initial fuel injection pulsewidth is determined by the ECU .however , the O2 sensor is now opertional and providing feedback from the exhaust gases which enables the ECU to adjust injection pulsewidth to maintain accurately a 14.7/1 air/fuel mixture . feedback from the MAP and PIP (engine speed) sensors will enable the ECU to adjust spark advances against load.the catalytic converter operates more efficiently in closed loop mode since a chemically correct air/fuel mixture is maintained.

• IDLE MODE OPERATION: the ecu will provide rich mix during idle to ensure that a stable idle is maintained.
  in order to achieve this the engine will be put into open loop mode . which means the signal from the O2 sensor will be ignored.open loop mode will have been selected by the ecu from input signal from the throttle position sensor indicating idle position.
  
• ACCELERATION MODE: This would be selected by the ecu when sudden increase in throttle position are signaled by the TPS and sudden change in pressure from the MAP sensor .In this mode extra fuel is supplied as the ECU increases the fuel injector pulse widths.
  
• DECELERATION MODE : This would be selected by the ecu when sudden decrease in throttle position are signaled by the TPS sudden changes in pressure from the MAP sensor , and excess fuel in the intake manifold .Excess fuel in the intake manifold  would be detected by the O2 sensor. In this mode less fuel is supplied as the ECU decreases the injection pulse width.