Emission is the most problem in all internal combustion engines, as they produce a lot of harmful gases which kills humans. Such gases as HC hydro-carbon, NOx nitrous-oxide, CO carbon-monoxide. Its a lot of systems been designed to control emissions such as EGR (exhaust gas recirculation valve) valve, oxygen sensor and catalytic converter. So emissions become a number one problem for planet earth, and that why a lot of manufactures trying to achieve best emissions for their vehicle and also starts to design alternative fuel engines, hybrids, electric, LPG and CNG.
Emission chec
k on cold start, engine r
uns rich as it warms up.
Slightly wormed up but still in open loop.
Warmed up engine, very good result for 200.000 kms vehicle.
In this case O2 and CO2 high as one of the cylinders receive no fuel it just produce O2 and CO reacts with it and make CO2.
Rich engine condition.
The catalytic converter is very important part of emission control, as it passes through it they convert itself from harmful gases to harmless, the only disadvantage of it as it has to be very hot to work for 100% and usually vehicle need to travel for 5-7 kms before it starts to work. So if people travel for 15 kms to work and back it only works half of the trip. With more technology cats are installed as close as possible to the beginning of exhaust to reduce heating time, but they still need some time and that is a fact!
Another thing is an Oxygen sensor, the most simple one had only 1 wire-signal for ECU, but now they can be found with up to 5 wires, usually one would be signal, second sensor preheat and two grounds for optimal sensor signal and preheat. This sensor tells ECU when ever engine lean, rich or stoichiometric .
Very important sensor as it regulates emissions and helps engine run as best as it can by controlling combustion at lambda 1 or 14.7 pieces of air to 1 piece of fuel. Its usually located on the top of exhaust manifold and operates at very high temperatures. The one we gonna test is Zirconia oxygen sensor with three wires, one is signal-white, 12 volts preheat power source-red and
black 
as a ground.
Oxygen sensor pattern. Voltage varies from top 0.8 volts to bottom 0.1 volts. Average voltage is 0.45 volts almost lambda 1, 14.7 to 1 air fuel ratio.
Sudden acceleration makes the engine run rich and same as sudden deceleration makes it run lean.
Top ends of the oscilloscope graph is when O2 sensor showing rich and bottom end of the graph is when O2 sensor showing lean.
Also on this graph we can see that each square divided by 1 second and from that we can see sensor output changes from lean to rich and rich to lean at roughly in less then 100 milliseconds, 0.1 of a second.
This is a Zirconium oxygen sensor and it work effectively only when it red hot and around 300 degrees C, it produce voltage up to 1 volts when oxygen ions passes through the sensor relative to outside air. When air fuel mixture lean its it produce low voltage around 0.1 volts, but when mixture rich its produce up to 0.9 volts.
This sensor looks in very good condition as it cycles from rich 0.9 to lean 0.1 when car operates at constant 2500 RPM's, also it changes rich to lean reading in around 100 milliseconds.
These days none of the workshops can perform all work without a scan tool, its an expensive piece of equipment but on late model cars such as BMW, Merc, VW and Audi when electrical fault occurs, you can not do anything without scan tool, it became a must have equipment for workshops. Late model cars comes with a lot of electrical equipment which can only be diagnosed with proper scan tool, other wise mechanic would be guessing whats wrong with car, but this guess can cost a lot for customer.We used Hanatech scan tools at Unitec to read and clear fault codes, read life data stream from sensors and actuators input and outputs.
Here is a life data from Ario's 1995 Honda Civic. The car running closed loop as we can see oxygen sensor working.
We scan the car for trouble codes and there is no faults in a system. So we disconnected MAP and TPS sensors, then scan the car once again and scan tool came up with two fault codes, MAP and TPS no signal.
Then we open current data and found that MAP sensor value changed to 0.3 volts and TPS voltage changed to 5.1 volts. We plugged plugs back into the sensors, and then deleted trouble codes. After scanning car once again no fault codes came up on a screen. So with the help of scan tool, which can point up towards fault direction we can fix cars faster and easier. Scan tool is an expensive piece of equipment, which can point onto faults, but it wont fix faults, as some technicians think.
This time we decided to use Unitec's car in case if we burn something... But nothing terrible happened. Anyway when working on fuel systems of the car everyone must take care of any flames, sparks and open fire around vehicle, not even welding around the corner, must avoid battery loose terminals as the can make a spark as well. And make sure you know where is fire extinguisher located as in case of emergency lots of people forget about it. Our one at the classroom and let it be there.Our specs for fuel pressure nobody knew so we took roughly guess of 200 Kpa at idle and around 400 Kpa at full throttle. We hocked up fuel pressure gauge to Nissan Primera 1992 with SR20DE engine and Steve done a mistake as he hooked it up back to front, anyway we fixed it and here we are, no leaks.
After we finished test plugged back all original fuel lines and checked for leaks, no leaks were found.
Its very important to test fuel system as it can give all sort of problems and when faulty under high pressure can split the hose and catch a fire from hot engine.
If the fuel pressure low it could work ok at idle or low speeds but if you put foot down it can only reach certain speed, had a torque lags at high RPM's range.
Low fuel flow can indicate work fuel pump and it will effect high range RPM's and performance.
High fuel pressure will make car run rich at low RPM's range and idle, black smoke at idle from exhaust, fuel economy would be lost and plenty of HC hydro-carbons will be produced making our world even worst by polluting.
And faulty fuel pressure regulator will make pressure ether High or Low constantly.
And again we use Toyota Corolla 4AFE engine and I'm using my own Corolla as i drive one to Unitec everyday.
Thats how our plug looks like.When did diagnostic on it came up with two fault codes, first one was 41 TPS sensor circuit and second was 21 Oxygen sensor. I found fault code description on www.ardio.ru website, which is Russian website for Scantool equipment and support. After inspecting both sensors in the engine bay i have found that somebody, we not gonna say his name, disconnected both plugs from TPS and OXY sensor. So I plugged them back, then pulled out EFI fuse from fuse box in engine bay and had a smoke outside while waiting for fault codes to clear. Connected my jumper wire in TE1 and E1, checked and found ENGINE CHECK light is flashing constantly, showing no faults found, amazing. My OXY sensor could make the car run in OPEN LOOP mode and never adjust rich and lean mixture for maximum performance and minimum emissions, and as my one is auto and TPS disconnected it could go into a limp mode and drive only on 3rd gear until it could see TPS or had a flat spots in acceleration while driving.
Petrol Fuel Injector Testing on Toyota Corolla 4AFE engine. 
Injector listening test, the most affordable and easy to do, even a long screwdriver can be used.
Second thing, we will check supply voltage to injectors and i showed that they all got approximately 13.69-13.7 volts.
Then we started the engine and back probe to injectors ground wire and connected our Uni-made LED tester to battery ground terminal (negative). When we touch ground wire of injector with engine running the LED light were flashing really fast even on idle and after increasing engine RPM's it went even faster, so that showed that all injector are triggered with ground wire and they all working properly and that with more engine RPMs frequency increases so they mast open faster.
shorter burn time. We can easily diagnose problem without removing any parts.
