WS7 Exhaust Gas Analysis (Petrol only)

Exhaust Analyser should be warmed up and recently calibrated when it,s time to start taking tailpipe readings put the analyser probe into the tailpipe and install exhaust fumes. Make sure there is adequate ventilation.

1. with the analyser probe sensing normal air, what are Four gas readings? Record the amount and then what it means:

CO        0.003             means:              Carbon monoxide
HC        6                    means:               Hydro Carbon
CO2     0.00                means:               Carbon dioxide
O2        20.84             means:                Oxygen

2. Start the engine idling code, and record the Four Gas readings Explain what is happening within the engine referring to the four gases:


CO      0.149 
HC      .230
CO2    15.03
O2       0.72


The amount of HC and CO gases are high as the calalgst cnverter is not hot to work and reduce the gases CO and HC.

3 .When engine has warmed up, recode the Four Gas readings: Explain what is happening within the engine referring to the gases:

CO               0.091
HC               47 
CO2            15.32
O2               0.64


The amuont of CO and HC gases dropped dramatically because the CAT is now hot and 02 and CO2 gases have increased.
Refaring to the fuor gases the engine is in good condation and the catalytic converter is working. the amuont of CO has drop from 0.149%  to 0.091% HC has drop from 230ppm to 47ppm CO2 has increased from 15.03%to 15.32% and O2 has drop from 72% to 0.64 %that,s means as the engine warms up there will be further drop in both HC and 02 and produce more CO2 and water H2o.


4. Run the warm engine at 2500 RPM, record the Four  Gas readings: Explain what is happening within the engine referring to the four gases:


CO                      0.109 
HC                      32
CO2                    15.50
O2                       0.37


The amount of CO gas increases just a little bit but HC is still declining and CO2 slightly increased it means the CAT is working perfectly and the engine is in good condition is will.


5. At idle the mixture rich with extra propane, LPG or carburettor cleaner, and record the Four Gas reading. Explain what is happening within the engine referring to the gases:

CO                           6.58
HC                           21.90
CO2                        14.90
O2                           0.63


Both CO and HC increased it means HC did not burn or incorrectly burnt produced a big amount of CO and HC so the engine is running very rich CO is slightly dropped and O2 gas slightly increased not enough time to burn all the O2 HC 


6 . At idle create a lean condition with an air leak record the Four Gas readings: Explain what is happening within the engine referring to the four gases:


CO                          0.003
HC                          15
CO2                        15.45
O2                           0.52


HC amount is high as there is not enough air to burn all the HC gases so the engine is running very rich and CO is low.


7. Accelerate the engine ,by blipping the throttle a few times and watch how the Gas reading change  Record the Four gas reading when the CO is highest: Explain what is happening within the engine referring to the four gases:

CO                       3.482
HC                       215
CO2                     13.65
O2                        2.21


Both CO and HC as the engine is running very rich once again there is not enough air to lots of O2 burn all the HC gases and the leakage causes for the oxygen to escape through exhaust pipe and does not react with HC molecules.

8. Disconnect one spark plug wire, ground it a jumper wire, then record the Four Gas readings as the engine idle: Explain what is happening the engine referring to the four gases:

CO                       0.041
HC                        17.08
CO2                      15.33
O2                         0.59


The amount of  HC is high because one of the spark plug lead is disconnected and dose not ignite so whatever amount of HC enters that cylinder goes straight through the exhaust pipe unburnt all other gases are steady.


9. If you can get to it ,disconnect the injector harness connector from one injector on an engine that has one injector for every cylinder: Record the Four Gas readings as the engine idles; Explain what is happening within the engine referring the four gases:

CO                     0.10
HC                      22
CO2                    11.26
O2                       6.26


 (1) O2 increased as the engine is not functioning properly it means there,s wrong or no signal input to ECU so this will cause wrong air-fuel mixture and will result wrong amount of gases produce.(2) Disconnect the injector harness has disabled that injector HC is 22ppm which is low because one cylinder dose not get HC whatever air enters that cylinder goes out with out any ignition that is why we get 6.26% of oxygen high amount.



Return the vehicle to good condition and proper adjustment.

11. Explain the different readings you would get from a vehicle with a catalyst converter and a vehicle with out one why?

The vehicle fitted with catalyst converter produces less exhaust gas emissions like HC ,CO and the vehicle which is not fitted with catalyst converter produce HC, CO gases because there,s no equipment  such as CAT to covert the unburnt fuel to H2O ,CO2 and N2.


12. Explain what light off point means and what happens?

Light off point means to get the catalyst  converter work it means the catalyst converter must get to a certain temperature  to start work get hot.


13. On lambda, O2 sensors why do they have 2,3,4 or 5 wires and what do these extra wires do?


Four wires and each wire have the fol living  function.
1.  Signal 
2 . Sensor ground 
3 . Heater supply 
4 . Heater ground