Mechanics

CHEVY 5.3 LITER

2004 Chevrolet Silverado • V8 4WD Automatic • 122,000 miles

I own a 2004 chevy silverado 1500 with a 5.3 liter eng. Recently the eng light came on and it started running really rough like it was going to die. It not only runs rough at idle but also in gear or hesitates when I excelerate from a stop. Ive done countless diagnostics, only to come up with multiple problems it could be. One was a possible blown intake gasket which I replaced and the truck ran fine for a little bit then the eng light came on and started the same thing. I also bought the 2 before cat oxygen sensors but havent installed the yet. Can anyone tell me what to look for or try from here?
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Gary George
February 15, 2011.




Let's start with what are the exact code number's you have?If you tell me those I can help you out.

Saturntech9
Feb 15, 2011.
P0131, p0171, p0300 these are the codes that I have.
Thank You, Gary
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Tiny
Gary George
Feb 15, 2011.
These are the codes that I have P0131, P0171, P0300
Thanks, Gary

Tiny
Gary George
Feb 15, 2011.
Let's start with the P0171 and p0300 code's I need to know if you have the hybrid engine or the regular 5.3 engine?Iam thinking since you replaced the intake gasket gasket and ran good for a little while you could have a warped intake manifold. Let me know what you have.

Saturntech9
Feb 16, 2011.
Also does it run any better from when it's cold to when it's hot?

Saturntech9
Feb 16, 2011.
I started the truck yesterday morning and it had a choppy idle out of the drivers side exhaust only, kind of like a thrushing sound. As it warmed up it was running that same way out of both pipes. It is not a flex fuel engine. It does have a electronic throttle body. I had the truck running and was checking for vacume leaks and noticed the throttle body blade pulsating back n forth a little, kind of like it was rocking back n forth. Is that normal?
Thanks, Gary

Tiny
Gary George
Feb 16, 2011.
If the engine has a vacuum leak for instance and the rpm is unsteady from that then yes the throttle plate would bounce around. Because the throttle plate move's to adjust the idle so it's try to adjust the idle and can't because of the poor way it's running. So how were you trying to check for vacuum leaks?The best way is to spray carb spray around the intake manifold gasket vacuum line's etc and watch for a rpm increase decrease or the engine die's out. If you have a scan tool that will read live engine data then take the scan tool hook it up to the truck select live engine data and watch the fuel trim while your spraying you will get a spike on the fuel trim if the engine suck's any carb spray in. Let me know what you find.

Saturntech9
Feb 16, 2011.
Well so far I took out the o2 sensors started the truck and it di run a little different but not for the better. I replaced them anyway and the truck still runs the same. I also check the fuel injectors by listening with a screw driver and they all sound the same. I checked the intake manifold gaskets and other vacume lines by spraying ether around them to see if there was a change in engine speed and nothing. I have chaged the plugs n wires awhile back but thats not sayin anything. I also thought maybe watered down gas so I put 2 bottles of heat in and nothing. I have a friend bringing over his fuel pressure tester, so thats next. Can you tell me what the pressure should be?
Thanks, Gary

Tiny
Gary George
Feb 16, 2011.
Have you tried taping on the mass airflow sensor lightly with a screwdriver handle to see if it die's or run's any different?The fuel pressure spec's are 385-425 kPa (55-62 psi) let me know what you find.

Saturntech9
Feb 17, 2011.
Reply to saturntech9,
So far ive checked everything that I could, injectors are fine great spark from coils, wires, plugs. Checked the mass air flow sensor, fuel pressure is 55psi, I bought a chiltons manual to help locate and trouble shoot. Showed a picture of the egr valve wich I dont think my truck has one. Since ive replaced the intake gaskets with felpro rubber gaskets would they be ruined if the intake is warped? I plan on ordering a new intake just to see and make sure.
Thanks, Gary

Tiny
Gary George
Feb 18, 2011.

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