Input Sensors/Fuel injection Engine Performance Input Sensors/Fuel injection

Objectives Explain the design and function of major EFI components as well as input sensors and actuators

Input Sensors Used to detect a mechanical position, chemical state, or temperature condition and change it into an electrical signal that can be used by the PCM to make decisions Main objective of engine control system is to control emission levels, fuel consumption, drive ability and durability of a vehicles engine.

Mass airflow sensor (MAF) Measures the amount of air entering the engine Located on the intake tube going to throttle body

Ford mass air sensor

MAF can be cleaned with approved cleaner

Air Temp Sensor (IAT) Cold dense air can burn more fuel than the same volume of warm air because it contains more oxygen Measures intake air temperature and sends electronic signal to computer The computer uses this input along with air volume input to determine the amount of oxygen entering the engine

Manifold absolute pressure (MAP) Some systems do not use a mass air sensor, this type of system uses a MAP sensor Measures changes in intake manifold pressure (vacuum) Closed throttle=high vacuum, low map value Wide open throttle=low vacuum, high map value

Engine Coolant Temperature sensor(ECT)(CTS) Monitors the engine temperature and signals PCM when the engine needs cold enrichment Usually located on the cylinder head or intake manifold Screwed into the water jacket in head or intake Controls open\closed loop functions of the engine

Barometric pressure sensor (BARO) Alters the air\fuel mixture and timing controls, depending upon the altitude at which the car is being driven At higher altitudes the air is thinner. Less air means the car needs less fuel. The baro sensor adjusts fuel mixture.

Engine position sensors(CMP-CKP) Cam\Crank sensor Tell the computer the speed of the engine and when the piston in each cylinder is on the compression stroke This input is used to set ignition timing and fuel injector timing as well The CKP sensor is also used to monitor engine speed

Knock sensor (KS) Converts engine knock vibrations into a voltage signal Screwed into the engine block Tells the PCM when detonation is occurring and PCM will retard timing as needed Worn engine bearings that are rattling will also cause timing to be changed

Oxygen sensors (EGO) Key sensor in closed loop mode Input is used by the computer to maintain a balanced air\fuel mixture Perfectly balanced fuel mixture 14.7-1 produces an output of .5 volt Lean mix .1volt Rich mix .9 volt Mounted on exhaust system # of sensors depends on manufacturer Can be located before and after catalytic converter

Oxygen sensor installed

Catalytic converter system and O2’s need to warm up quickly in order to be most effective at reducing emissions. O2 located after catalytic is used to monitor performance of converter.

Open loop ECM calculates air/fuel ratio based on inputs from the coolant and MAF sensors and ignores the other engine inputs The engine managment system (PCM)will remain in open loop until engine reaches operating temperature The oxygen sensor also has to get hot enough to operate properly Some oxygen sensors have a built in heater in order for them to get to operating temperature faster No feedback to PCM This type of condition usually happens when engine is cold

Closed loop Sensors provide constant feed back to PCM The PCM makes calculations based on input sensors PCM tries to maintain a air/fuel mixture at 14.7 to 1 Closed loop occurs when engine is at operating temperature Benefits-Better idle quality, more power with less fuel, and reduced emissions

Throttle position sensor (TPS) Informs the computer about the rate of throttle opening .5-1.00 volt idle speed 4.5volts WOT Common symptom of a bad TPS is a stumble or hesitation Mounted on throttle body

Vehicle speed sensor (VSS) This sensor tells the computer the vehicle’s speed in MPH Usually mounted on transmission tail shaft or transaxle housing

Adaptive strategy PCM can learn from past experience This feature adjusts for worn or misadjusted sensors and ensures that the engine will operate normally With adaptive learning, a short period is necessary after the battery has been disconnected Engine may surge, idle fast or have a loss of power. Average learning period lasts for five miles of driving

What if there is a problem present? Check engine light will come on

Questions to ask the customer When did the light come on? How is the vehicle running? Has anybody else worked on it? These three simple questions could save you a lot of diagnostic time.

Test drive!!!!!! Diagnose Test drive the vehicle and verify the complaint Look up any TSB’s (Technical service bulletins) on vehicle (especially important when working with emission equipment) some parts have 100,000 mi warranty Hook up diagnostic tool to test port

OBDll test port locations

Diagnostic Scanners Many different manufacturers Prices range from $40-$8000 Least expensive scanner only read codes –no data

Example of diagnostic trouble code P0440 –Evaporative system malfunction-gross leak detected Solutions Remove and reinstall the gas cap, clear the code, and test drive and see if the codes come back. Inspect the EVAP system for cuts/holes in tubes/hoses Inspect for damaged or disconnected hoses around the Evap purge solenoid Check and/or replace the sensor Check and/or replace the purge valve Have a professional use a smoke machine to detect leaks

P0300-Random/Multiple Cylinder Misfire Detected Faulty spark plugs or wires Faulty coil (pack) Faulty oxygen sensor(s) Faulty fuel injector(s) Burned exhaust valve Faulty catalytic converter(s) Stuck/blocked EGR valve / passages Faulty camshaft position sensor Defective computer

Repair After replacing or repairing faulty component make sure to clear all codes Test drive vehicle Pull car back into shop and recheck for codes If no codes then car is ready