I have a 2000 cummins 4x4 with the 5 speed manual. I have a all stock truck, except for straight pipe and I replaced the VP44 last year along with a Airdog 100. It will surge mostly at idle my lights will go bright then dimer back and forth driving me nuts. Also noticed my fuel mPG are in the 14 range. Any help would be great thanks.

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Anyone

 

mine will do that at idle when i first start it while its cold out. from the grid heater kicking on and off. after it warms up it's good unless i turn it off then when i turn it back on it'll do it a couple times then stop.

 

Mine does it after its warmed up, it does it all the time.

 

Just to start stupid simple I'd try disconnecting the grids and see what happens. throwing any codes?

 

Mine does the same thing specially when its cold out but once she is warmed up it stops prob just the grid heater kickin on and off like they said above