G1900 Diesel Rough Idle

[charliet05]

My 1st Kubota. A G1900 with 1340 hrs.

Engine runs great from about 1/3 throttle to full throttle movement. Unit mows great and seems to have enough power for the 54" mower.

I crank the engine with the throttle (lever) at minimum. It will fire up within 3 - 5 seconds. But it idles really rough. Engine will run smooth after moving with the throttle at about 1/4 - 1/3 of movement range( even when cold). Will idle just as rough when bringing the throttle back to minimum after 3+ hours of mowing. I have been told by a diesel mechanic that all the Kubota diesels he has seen runs very smooth from idle to full throttle.

New fuel filters. Air filter "looks OK"; cleaned a couple of times with compressed air. Engine does not "smoke" (white, blue or black) when mowing.

We have three older diesels farm tractors (non-Kubota). They all run rough for a few minutes upon starting but will always idle smooth when warmed up and after several hours of use.

Any help will be greatly appreciated.

Charlie

 

[Big Kahuna]

I bought a G5200 in 1994 new and it always bucked when at idle till about 1/3 throttle, Mom uses it now, 19 years later its still the same, might be the way they are, it mows great and has no loss of power so keep on running.


Big Kahuna

 

[kc8fbl]

Does it just shake the tractor? Mine idles fine, but will shake the tractor from the engine torque. If I speed the rpm's up to 1000, everything smooths right out.

You may want to run a little diesel injector cleaner through it too when you fill up next.

 

[kuboman]

Is the idle set too low. Some 2 and 3 cylinder diesels will shake themselves to death if the idle is too slow. Do you have any way to check the idle. Or do you think it is a missfire on 1 or more cylinders.

 

[charliet05]

Yes, it shakes the unit quite a bit at idle. My biggest concern!

kuboman, I think the idle is too low. What is needed to check the idle? When the ambient temperature is cool (50 deg f), I think it is miss firing. Sounds like our older IH diesel tractor (3 cylinder) when starting in cold weather using the "start position on the shutdown lever". The IH idles very smooth after warming up. G1900 will not!

 

[ThisIsNotaStep]

I have a BX with the exact same issue, idle shakes so bad I have had to reweld the air cleaner loop braket twice already, read here once, the motor mounts were at fault and a dealer upgrade was available .. watching for your answers ..

 

[kc8fbl]

You can follow your throttle linkage down to the injector pump and there is a screw you can tighten or loosen to adjust your idle. I believe there is a nut there to lock the throttle. I believe tightening it will increase idle. Just turn a little at a time, then rev up and bring throttle lever back down to idle and see if it changed. You might try calling the dealer and see if they can print you a diagram on how to adjust it too.

 

[mwest479]

Is the idle set too low. Some 2 and 3 cylinder diesels will shake themselves to death if the idle is too slow. Do you have any way to check the idle. Or do you think it is a missfire on 1 or more cylinders.

Kuboman , Have a L-175 , has started shaking at idle. If throttle speed is increased shaking stops. Tractor does not smoke. How can you tell if an injector is faulty or cly is misfiring for some other reason ? I am going to increase the idle speed to see if this stops the shaking.
Thanks , Mike

 

[kuboman]

Kuboman , Have a L-175 , has started shaking at idle. If throttle speed is increased shaking stops. Tractor does not smoke. How can you tell if an injector is faulty or cly is misfiring for some other reason ? I am going to increase the idle speed to see if this stops the shaking.
Thanks , Mike

It is unusual that there is no smoke with a misfire. You can check by loosening off the pipe at the injector and see if there is any change in how the engine runs. As you loosen each injector one at a time the engine will run really rough and want to die until you come to the one that is not functioning properly. Then the change will be minimal or non at all. Remember to cover the injector with a rag as you loosen as the diesel is under high pressure.

 

[charliet05]

kc8fbl,

Followed your suggestion. Had to turn the screw (bolt) a little more than anticipated to increase idle rpm's. But, it idles a "whole lot better" now! Solved my problem!!

Appreciate all replies. Good site!!!