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jcook, Small Engine Technician
Category: Small Engine
Satisfied Customers: 120
Experience:  15 yrs experience John Deere C&CE technician. Briggs & Stratton MST, Instructor
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I have a Deere Gator XUV 620i, FD620D CS26 DFI kawasaki

Customer Question

I have a John Deere Gator XUV 620i, FD620D CS26 DFI kawasaki engine. At about 130 hours on the machine it has started to run unevenly at low speeds. Mainly at speeds under 10 mph. On a cold start it does not have the problem but as the engine reaches normal operating temperature it starts the low speed uneven rpm problem. If I take it on the open road at 15 to 30 mph it seems to run normal. Have replaced plugs, air and fuel filters with no change. The original plugs look like an almost black dry carbon color. Possibly not as tan in color as I would like to see them. What should I check/try next?
Submitted: 7 years ago.
Category: Small Engine
Expert:  Carey (Turtle) Moore replied 7 years ago.
Chat Conversation Started
Carey (Turtle) Moore :

Does this engine surge more or uneven as you say if you are trying to hold and maintain a certain speed. But is not as noticable powering all the way to top speed?


Yes, it runs unevenly when I try to maintain a certain low speed, say at a throttle position about 5 mph. If I need more throttle because of an uphill or just because the trail is straighter then it seems to be running normal again. By running uneven I mean the rpm drop to almost idle rpm and its like it at deceleration and then the rpm pick up and it surges back to the throttle position speed.

Carey (Turtle) Moore :

Sounds like a governor issue or loose linkage or play in throttle linkage bewteen the governor and carb. Check the holes that the links go into for wear. Jack the rear wheels of the ground and run and locate the throttle shaft to see it it is moving back and forth quickly while you hold a steady slow rpm.

Carey (Turtle) Moore :

It been a long day and my spelling is off. Sorry


This engine FD620D CS26 has a direct fuel inject pump and I believe does not have a mechanical governor. There is no linkage at all that goes to a governor from the throttle body. I think the speed/rpm is controlled electronically. Actually it has a speed limiting switch that limits it to 20 mph if used. Its top speed is 30 mph and I do not know the rpm ranges at these limits. I can take a photo of the intake and send it to you if you like. It has the throttle body with controls and sensors that limit and air and injector output I believe.

Expert:  jcook replied 7 years ago.
There are a few situations that will cause surging on these units, If there are no fault codes flashing on the dash then there are a few things tou can check, First the rpm is controlled by the ECM on these units If the fuel is over 30 days old then get rid of it and install fresh, Secondly check the ground for the ECM. It is located on the frome beneith the passenger seat, and is held in place with a self tapping screw, make sure it is clean and tight. Make sure the oil level is not over filled and dilluted with gasoline. If all these things check good then the issue will be in the throttle body, There are TPS sensors that read the throttle position. When they act up they will not always flash a code. Make sure no one adjusted The throttle stop. It should still have the paint markings on it and be undisturbed. Everything else that will cause this will have to be corrected at a dealer. I have had severial throttle body issues with the 620's. If you have to use your dealer have them reveiw DTAC solution # 81639, This will more than likely solve the issue. Unfortanitley it will have to be done by the dealer, In the past deere tech support will have to be contacted to get a throttle body. Talk in a bit.
Customer: replied 7 years ago.
Checked the things you suggested and everything is O.K. Took it into the local John Deere dealer yesterday and will let you know what they find.
Expert:  jcook replied 7 years ago.
They will be able to refer to the bulletin I listed. It should solve your issue. Talk in a bit....
jcook, Small Engine Technician
Category: Small Engine
Satisfied Customers: 120
Experience: 15 yrs experience John Deere C&CE technician. Briggs & Stratton MST, Instructor
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