Backfiring from full throttle to idle

[kenneth2]

I have a 15 year old walker with a Kohler ech740-3031 with fuel injection. Backfires badly from full throttle to idle. I have seen discussion on shutting down at half throttle. I never had this problem before. Spark plugs a little sooty, anything I can do with Eli to make it run leaner. Spark plugs were 2 heat ranges too cold. I can try replacing first.

 

[Craftsman Garage]

I have a 15 year old walker with a Kohler ech740-3031 with fuel injection. Backfires badly from full throttle to idle. I have seen discussion on shutting down at half throttle. I never had this problem before. Spark plugs a little sooty, anything I can do with Eli to make it run leaner. Spark plugs were 2 heat ranges too cold. I can try replacing first.

This is usually normal to some extent because when you lower it to idle, you are blocking the air from entering, which sets the mixture uneven temporarily, and that unburnt fuel is pushed into the hot muffler where it explodes. It wouldn't backfire if you always kept it at full throttle as you should Idling is bad for these engines.

 

[Craftsman Garage]

I have a 15 year old walker with a Kohler ech740-3031 with fuel injection. Backfires badly from full throttle to idle. I have seen discussion on shutting down at half throttle. I never had this problem before. Spark plugs a little sooty, anything I can do with Eli to make it run leaner. Spark plugs were 2 heat ranges too cold. I can try replacing first.

I don't know much about small engine EFI systems, but maybe something to do with the injectors or an o2 sensor?

 

[Auto Doc's]

If spark plug heat ranges are that cold, put the correct plugs in. People tend to think spark plugs are all the same, but they are not.

I used to see this issue on gas engine farm tractors quite often. The hotter the engine gets the worse it will pop and snort.