Q5 4.3 sputtering after turning off ignition

[maddog2112]

This question is for a friend of mine. He has a 09 Q5 with a brand new 4.3 used one whole season. We were at the lake sunday and his engine would kick and sputter for 5 to 10 seconds after shutting it off. I remember that from the old 70`s cars, but it`s been so long, I can`t remember what causes it. He has the carbureted model. Thx

 

[beautiful dawn]

Re: Q5 4.3 sputtering after turning off ignition

This is common in carbed 4.3 ltr marine engines. Two things will help. (1) Let the engine idle for about 30 seconds to a minute after running at speed. This is the cheaper of the two methods, although it can be tough to do when partaking of water sports. (2) Use high octane fuel. The sputtering is called dieseling or run-on, and is caused by carbon build up on the top of your pistons. It gets very hot when the engine is running and will act like a glow plug in a diesel engine, when you turn the engine off the glowing hot carbon will ignite the residual exhaust gasses in the cylinders. this will continue until the exhaust is all burnt. Higher actane fuels do not leave as much carbon and reduce and eventually elimate dieseling. It will not however make your boat go faster.

 

[maddog2112]

Re: Q5 4.3 sputtering after turning off ignition

beautiful dawn, makes sense. I`m surprised I haven`t heard of this problem more often. Thx

 

[supercrewser]

Re: Q5 4.3 sputtering after turning off ignition

Make sure the rpms are at 650 that will help also. I had the same thing start on my 2010 q5 after i filled it up on its 3rd tank of gas from the marina. I backed off the idle set scew a 1/4 turn and it did ti once and since i refueled it hasnt happened. Go figure.

 

[maddog2112]

Re: Q5 4.3 sputtering after turning off ignition

Thanks supercrewser, I`ll suggest that to my friend.