Rough running tractor

[Rob REECE]

I have a 2009 John Deere 4320. When I start it up it runs smooth for a couple minutes then the engine starts to speed up and slow down. I changed the fuel filter and bled the system. I changed the air cleaner filters also.

 

[thepumpguysc]

I’d have to guess that the flex ring has broken up inside the inj pump and the engine is getting ready to run away..
Unless it has had the updated weight retainer installed or the inj pump name plate starts with “DM”..
I’d stick with broken flex ring.