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I have a 05 Impala Base 41k on it and lately I have developed a intermittent starting issue sometimes it cranks up just fine it got worse when the weather got cold. It dose not stall or no Security Light on nothing like that so I know that passlock is ok. I have no aftermarket alarms remote starts nothing everything stock. But lately I have to step on the gas in order for it to crank I have researched all of the GM Fourms and I have heard everything from Fuel Presser Regulator to Crankcase Sensor etc. I have no clue Also I discovered that while it is in ACC mode parked the battery drains down so I think that it is a issue with the voltage somewhere. I have not had the fuel filter changed but don't want to spend money if I don't have to. Anyone have any Idea'*

try turning the key to run a couple times slow let the pump prime see if that changes how it starts. the fuel filter isnt that much and its easy. it sounds like its starving for fuel. if that doesnt do it i would check the fuel pressure see if thats in spec.

I would start with tracking down your draw problem. If your turning the key and have nothing then it'* not a sensor. Look in tech info here under testing, we have a Amp draw test in there, easy to do. Find that and you may correct this problem.

Mine was doing the same thing,replaced fuel pressure regulator and fuel filter while i was at it.look around pressure regulator to see if any fuel leakage.It sounds like yours is cranking over but just not starting

is the security light flashing if it is it will be fine till around 100k what you need to do is turn the key on wait till the light stay on turn key off and started up if it not then check fuel

sorry there is one other thing i forgot about the is two wire behind the intake that will short out. it will finely weld to intake and could your fireing sensor go out took my mech. two week to fine the problem

If you have to goose the throttle a little bit, good chance its the IAC(inlet air control valve). Sounds like its not opening up far enough to allow air to bypass the throttle plate while starting.