Engine surging

[diggla]

I have been noticing for some time that when my truck is at idol or i am driving at a cruise speed on the highway all of my lights are surging. when at idol you can hear the engine sound as if it is surging up and down in rpms but they are staying the same. I have recently replaced the alternator and both batteries on this truck. whats the prob??



2002 f-350 XL superduty 7.3L powerstroke turbo diesel ..180000km STOCK

 

[Tail_Gunner]

I have recently replaced the alternator and both batteries on this truck.

How about the serpentine belt, tensioner and idler pulleys?

 

[diggla]

No i havent replaced any of those , my belt seems fine. how can I tel lif the pullies etc... are bad??

 

[Johnswiftm]

Check your alt. output.

 

[whatabudro]

Also chep the IPR. It can cause this.

 

[diggla]

IPR??