JuanB 
SS Member
Posts: 3,842
Registered:
5/5/03
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From: TX
Truck: 2004 Sierra
Mods: 19
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11/3 12:17p
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All of a sudden my truck is misfiring at idle. Fuel mileage is down.
How do you check Fuel pressure at the fuel rail petcock? It not the standard "Bike" Valve
Code was cleared and returned. Could it be the Fuel Pump??????
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Stevens07
Supercharged SS Member
Posts: 14,722
Registered:
3/18/03
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From: PA
Truck: 2007 Sierra
Mods: 14
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11/3 12:48p
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Clean your maf sensor, clear the code and see if it comes back.
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JuanB
SS Member
Posts: 3,842
Registered:
5/5/03
Status:
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From: TX
Truck: 2004 Sierra
Mods: 19
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11/3 2:30p
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Ok Steven Thanks. Maf sensor cleaned with Maf cleaner and cleared the code 0300 and still get DTC. All Help is Really Appreciated Guys...JohnB 
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JuanB
SS Member
Posts: 3,842
Registered:
5/5/03
Status:
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From: TX
Truck: 2004 Sierra
Mods: 19
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11/3 2:51p
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This describes my problem to a T. Thought I heard a Funny Noise from the Fuel pump the other day.  YUCK
And Deer Season starts Saturday!!! YUCK YUCK CRAP
Lean Misfire
The lean misfire is another common reason for an engine "miss"—this is due to an imbalanced air/fuel ratio (too much air). Since an engine needs a richer (more fuel) mixture for a smooth idle, this problem is more noticeable when the vehicle is idling. The lean misfire may decrease or disappear as the engine speed increases because the efficiency of the volumetric flow into the combustion chambers increases dramatically. This is one reason why a vehicle gets better mileage on the freeway than in the city. An EGR valve that is stuck open, a leaking intake manifold gasket, a defective mass air flow sensor, a weak or failing fuel pump, or a plugged fuel filter are some of the many causes for a lean misfire.
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98z71chevy
Heavy Duty Member
Posts: 662
Registered:
8/9/06
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From: PA
Truck: 1998 Silverado
Mods: 9
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11/3 3:31p
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P0300 Random cylinder misfire... try a can of seafoam in the gas tank.
I know from experience!!!
Gill
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Wheatley
Supercharged SS Member
Posts: 7,878
Registered:
6/27/03
Status:
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From: TX
Truck: 2006 Silverado
Mods: 10
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11/3 10:39p
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Hey John how are you?
I am going to say it is the pump going south.If the pump is going bad the engine will not get the amount of fuel needed and run lean,therefor cause misfires!!
When you replace the pump,also replace the regulator.You really don`t have to but it is a good idea to.If you need more help let me know.
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JuanB
SS Member
Posts: 3,842
Registered:
5/5/03
Status:
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From: TX
Truck: 2004 Sierra
Mods: 19
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11/4 8:59p
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Hey Charlie, Glad to Here From Buddy 
Well I replace the Fuel Pump and Fuel regulator and cleared the code.
It still was running rough at idle and threw a p0303 Which told me there was an issue with cylinder #3. Removed the pretty new E3 spark plugs and replaced with a NGK I had and problem is Solved. MSD wires were checked also to be Good
At least I wont have to worry about that funny Fuel pump noise from the other day. Ala in all I a Happy Camper, A Hunting I will Go 
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Wheatley
Supercharged SS Member
Posts: 7,878
Registered:
6/27/03
Status:
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From: TX
Truck: 2006 Silverado
Mods: 10
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11/4 9:31p
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Oh man,never run those plugs.LOL
they are a joke
Stick with the good ole NGK like you have now or the stock delco platinums and you wont have trouble.
Great to see it is solved.
look at the brite side,you have a new pump now!!LOL
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