my buddy has an 03, 3500 6 speed, has a bully dog chip, exhuast intake.... stock other than that. the idle is jumping all over the place, it wants to die, then keeps goin then wants to die? whats the deal? they just re-did all the fuel system and put a new sensor in the petal. what would want to make it die like that? it will drop rpm then jump back to normal. not like once a month like every 5-10 seconds. thanks for any help it threw a code but the code was like relay for some kind of clutch, not idle or fuel

 

My guess is that the lift pump is going out. Does he have a fuel pressure gauge?

A Bully Dog will pull fuel pressure down to Zero. So will my Smarty if I let it do it, which I don't.

 

Could be a sticking FCA valve on the CP3 pump. Quick way of testing it is to fill the fuel filter canister will 2 stroke mixture oil. Start the engine and let it idle. If it doesn't lope that's most likely the problem.
Another way of testing it is to remove the valve and shake it. If it doesn't rattle it's bad.

MikeyB

 

the chip isnt on when it doin it, it just had a brand new lift pump put in 2 months ago. it only does it at idle, my buddy doesnt have a FP gauge yet i told him he needed one.