School me on 5.3 running lean

[throttlejunkie]

04 silverado started running like hell! Spent alot of time and money today chasing a lean condition and, misfire
I know that's kinda low on the info, I'll add more. Any thoughts comments or sugestions let me here em.

 

[wannabe]

put a fuel pump on it and your good. or there is a small chance its intake gaskets. but 90% of the time fuel pump

 

[wannabe]

put a fuel pressure guage on the test port on the pass. sside and unplug the vac. FP regulator and plug it off. see what readings your getting. anything under 50psi at idle is bad pump. have seen a REALLY clogged fuel filter do this ONCE, slim chance thats it

 

[wannabe]

and to check for the intake leak just spray brake cleaner everywhere and see it if idles up, but usually if its intake gaskets it will act up worse when cold and run fine when hot.... ok i think that is all for now

 

[grcthird]

Any DTC's? Clean your mass air flow meter if you run a K&N, the oil gets sucked onto the filaments and gives incorrect info to the ECM.

 

[wannabe]

I'm guessing system too lean bank 1 and 2 and a random misfire

 

[throttlejunkie]

Tried the spray around the intake...nothing, fuel pressure is 50+ when key is on and engine off, when engine is running its 44 psi, disconnect the vacuum on the regulator and it jumps to 52psi. Its was mild stumbling and misfiring to begin, now its undriveable. Changed fuel filter and emptied the fuel, replaced with fresh, no change hell its worse. New plugs and wires also.

 

[throttlejunkie]

Also running k&n and cleaned mass air.

 

[grcthird]

Looked at the EGR valve to see if it's stuck open?

 

[Bumpers]

Re: Re: School me on 5.3 running lean

04 shouldn't have egr.. I'm surprised it had a fuel filter since they quit using them in 03 unless your talking about the sock in the tank. Have you drove it with the FP guage on to see if it drops out or anything?

sent from a payphone

 

[Bumpers]

Re: Re: School me on 5.3 running lean

Also check the ground for the coil pack harness I believe its behind the intake on top of the block .. I know ground issues in those trucks can drive you nuts. What codes is it throwing?
sent from a payphone

 

[civicmindedex79]

Am I off on thinking the rail should keep 58 psi all the time atleast?? 44 psi sounds a lil low to me

 

[throttlejunkie]

That's what I'm hearing on the fuel, but is that pressure difference enough to make it run like crap? Its stumbling and missing something awefull now. Ill take a look on that ground, also the fuel filter apparently is straight up a mystery on this truck. Call any parts store around and they say they ain't one...BUT...I never thought it had one either til my old man crawled under and saw it, I called BS but sure enough, had to call chevorlet to find one.
Pulled the codes, wrote em down, ill have to see which ones exactly. Seems like one fur sure was p303, or p300..both banks lean and cylinder missfires

 

[yankster]

I've seen this more than a few times and it was the intake gaskets every time. My 6.0 wouldn't idle up spraying fluids on the intake because it was leaking under the intake above the windage tray. It threw random misfire codes and lean on bank 1 and 2. The gaskets are really easy to change. The parts stores make a gasket called a "problem solver" due to the regularity of the issue. They cost more but have a thicker rubber ring to ensure no leaks.

http://www.autozone.com/autozone/parts/Felpro-Intake-Manifold-Gasket/2004-Chevrolet-Silverado-1500-4WD/_/N-jlycrZaliz2?itemIdentifier=217565_259699_19388_

 

[85toyo]

I've seen this more than a few times and it was the intake gaskets every time. My 6.0 wouldn't idle up spraying fluids on the intake because it was leaking under the intake above the windage tray. The gaskets are really easy to change. The parts stores make a gasket called a "problem solver" due to the regularity of the issue.

X2 A friends 5.3 does the same thing because of the intake gasket

 

[throttlejunkie]

Preciate it guys, I reckon Friday I'll be swapping some intake gaskets. It definitely makes scense for the way its acting.

 

[musselman]

Before you pull the intake off pull the exhaust down at the manifolds sounds like stopped up cats real common on those trucks.

 

[Blase]

Fuel pressure is too low. 58-62 is what it needs to run correctly. Anything under that and you will notice it running bad. I'd start by fixing the fuel pressure issue.

 

[yankster]

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[throttlejunkie]

I've thought about the cats, but would that come on so sudden?? Also, I see the pressure is a little low, but would that cause the injectors to fire that poorly, casue its having a hard time even idling now. Its straight up acting crappy now!