Why does a gasoline engine continue to run dieseling after ignition is turned off?

Answer

Because you have carbon buildup. By federal law only 95% of gasoline has to ignite, or burn. So every time you shut off your engine, when those injectors give one last burst of fuel after the key was turned off, that little 5% in that hot engine ends up turning into carbon build up, which sticks to your internal fuel system components. (top of pistons, fuel chamber, ect.) In time, (Usually a LONG time, MANY miles) that carbon build up actually prevents the piston from compressing the way the manufacturer intended it too, which causes the "dieseling effect". You can have your vehicle serviced at your local dealership, ask them for a "major fuel service". This will clean out all that acumulated carbon and allow your engine to run as it was intended. OR, you can try using the next higher grade of gasoline next time you gas up. But this will only prolong the inevitable. This is all assuming of course that we are dealing with a newer computer controled vehicle that does not require manual timing adjustment. Hope this helps.

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