Very rapid light surge under light loads

[hardhat]

2011 f series with 125 hours. Works great. Love the machine. Had a tiny leak of hydraulic fluid on the return line from the fan due to loose fittings. No problems with machine.

When the engine is under light load (cruising on level terrain or slight incline), it surge very slightly. Can't feel it, but can hear it (can hear rpms cycle very rapidly (3-5 times per second). Rpms don't go up or down much according to tach. If I raise rpms or put machine under heavy load, it goes away.

I am assuming this is normal operation as I have heard other diesel engines do it. Anyone know what causes it? Almost seems like has to be related to speed control on the computer.

Thanks

Larry

 

[mtb70]

Could be the A/C Compressor cycling on and off. It is normal, will effect engine RPM's and probably more noticeable under light loads. Computer doesn't control engine speed. Turn off the A/C and see if the condition goes away.

 

[DEWFPO]

It could be the Horsepower Management mode if you are set to 1 (default). Set it to "0" and see if it goes away.

DEWFPO

 

[hardhat]

Thanks. Had not thought of that.

 

[hardhat]

It could be the Horsepower Management mode if you are set to 1 (default). Set it to "0" and see if it goes away.

DEWFPO

That was it
thank you very much

 

[HL649]

It could be the Horsepower Management mode if you are set to 1 (default). Set it to "0" and see if it goes away.

DEWFPO

I have the same problem as hardhat described but my Toolcat is a 2007 "D" Model. Is this Horsepower Management mode something that I have on my '07? How do you change it?

Thanks.

 

[DEWFPO]

I have the same problem as hardhat described but my Toolcat is a 2007 "D" Model. Is this Horsepower Management mode something that I have on my '07? How do you change it?

Thanks.

My '09 D model has it, your '07 probably does as well.

Toolcat HP Management :

The User Manual (pg SA-6 for the "D"), states:

The key switch must be OFF and the engine stopped to enter setup mode.

Press and hold the SPEED/HOURS/RPM button until the display screen lights up.

Press the S/H/R button repeatedly until "HP" shows on the display.

If "HP 0" is shown, the HP Management function is OFF. If "HP 1" then HP Management is ON.

Press the WORK button to toggle between ON/OFF.

Press and hold S/H/R button until "donE" appears on the screen. This will save your settings.

DEWFPO

 

[Spudgunner]

BTW, should your RPM sensor ever go bad, this is a good way to circumvent it's invalid input to the onboard computer. That is, turn HP management off. Saved my bacon once upon a time in the middle of winter. My TC is an '07 "D".

 

[hardhat]

After turning HP management off, I noticed that it still does it. I thought it had gone away. I don't really think it is abnormal. I have heard diesel engines do this before. I don't notice it a lot of the time. The surge is not enough to feel at all, just can hear it. Under more load, or changing loads it goes away. I have turned hp management back on as i like the way the machine runs better with it on.