up and down idle

[Duroman]

I have been having the engine sounds like it lopes . The tach doesn't jump . What could be causing this . I changed fuel filter Please give me ideas ?

 

[2004LB7]

fuel pressure regulator is a common culprit. don't use any aftermarket regulator. only genuine bosch

air in the fuel supply lines can cause it too

 

[Duroman]

I have heard of that . Where is it located and what is involved ? Thanks for the help !!!

 

[2004LB7]

this is probably one of the best write ups I've seen

[Guide] LB7 Fuel Pressure Regulator Replacement

www.duramaxforum.com