Idle problems

[JohnnieBishop]

Got a 2003 Ram 2500 Cummins with NV5600 manual trans, and when I have my air conditioning on coasting down the road with my clutch pressed getting ready to slow down, the truck fluctuates in rpm from 750-900. Have no problems with the ac gets real cold. Also checked my codes at work no codes but it says my check engine light should be on with engine running.



Any help would be greatly appreciated.

 

[6speed]

Mine does the same and its an 04. But as soon as I touch the brakes it goes to 750

 

[JohnnieBishop]

mine does too. I just replaced my fuel filter and see if that helps. also disconnected my battries for an hour from both positive and negative. also someone told me it might be the throttle position sensor.

 

[jhenderson]

If you put it in neutral with the truck moving more than 15-20 mph it will idle up as you describe. No matter if the clutch is in or out. It has to do with the ECM

 

[ABennin]

My 2000 idles around 850 in neutral coasting down the road. Once I slow down under 5 mph then it idles around 820 and with the air on around 800. It has done this as long as I have owned it. I would consider this normal.

 

[JohnnieBishop]

fuel filter and disconnecting the batteries didn't help any. not sure where to go from here.

 

[rbattelle]

Check the wiring harness at the AC clutch for chaffing and grounding out. Then check the fan clutch wiring harness where it runs up against the radiator on the passenger side. Shorts in those wires can cause some strange issues.



Having said that, it is normal to idle between 800 and 900 rpm with the brakes released, the engine decoupled from the wheels, and vehicle speed above 5mph.



-Ryan