The deposits were collected from different parts of a gasoline direct injection (GDI) engine， such as electronic throttle body (ETB)

inlet manifold and its flap

inlet valve

inlet valve seat

piston crown

etc. The collected samples were then analysed by thermogravimetric analyzer

including the volatilization weight loss analysis and oxidation weight loss analysis. In order to get a clearer of the content of each understanding component of the collected samples

the volatile weightlessness was divided into volatile weightlessness

semi-volatilization weightlessness

and non volatile weightlessness. The results show that all collected samples mainly contain volatile organic compounds

wacromolecule components

solid carbon and ash

while there is almost no solid carbon in the ETB deposit sample. Most of the deposits are volatile organic compounds mainly from engine lubricating oil

except the deposits of inlet valve and piston crown

which have a high ash content

accounting for almost half of the total deposit weight. In summary

the deposits collected from GDI engine mainly come from engine lubricating oil

combustion chamber back-flow exhaust gas and suspended particle in the atmosphere

where the throttle valve is less affected by the back-flow exhaust gas.