Hello - brand new to the forum but wanted to reply to your 825 rough idle issue. Our issue was that the engine would idle slightly low (940-960 rpm) and sort of sputter. When the throttle was depressed, the engine would struggle and cough until it reached 4000 rpm with no load. After roughly a minute. The idle would increase and become steady. The machine would then run ok but lack some power. Plugs were ashy, slightly grey, indicating a lean condition. No diagnostic light would flash. I fixed the issue by testing the fuel system and ultimately replacing the fuel pump. To test fuel pressure, install a mechanical gauge after the grey inline filter. JD spec fuel pressure is 40-50 psi. Pressure should build quickly when the key is turned to the 'on' (not run) position. Our machine was running (albeit roughly) on 10 psi! There is no logic in the ECM to monitor fuel pressure; the ECM just says "ok, it should be 40-50 psi" and I believe it uses info from the O2 sensor to 'fine tune' fuel delivery. This would explain why the idle condition stabilized after the ECM had an adequate fuel map, but please understand this is speculation on my part.
The issue may not be a fuel pump issue. It may also be either a clogged filter on initial pickup filter (under the pump) or the fuel regulator, which is located above the fuel pump. The fuel regulator also has a screen. Ours was very clogged. The fuel reg can be removed by removing the hair pin from the mounting assembly and I cleaned the basket with carb cleaner and let it dry. Anyway, our issue was a worn out fuel pump. Again, no code because no logic in the ECM to monitor fuel pressure.
I've found the forum to be very handy; we have 4 gators to maintain out here. Wanted to contribute our experience for the good of the group. Hope this helped.
