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2004 Silverado 1500 5.3 Random Misfire HELP!!!!

2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby mxz600rr [OP] » May 11 2013, 12:05am

Hey Guys,

So i am having a major issue with my 2004 Silverado 1500 5.3L with 210,000kms, It all started about 6 months ago when it started sputtering and throwing the P0300 code (Random Misfire). So first thing i did was change the plugs and wires and that didn't do anything. We found out that who had ever owned it before me must have ran some bad gas because the injectors were completely clogged with black powder. So i replaced all 8 injectors with brand new AC Deleco ones, cleaned out the fuel rails and dropped the tank and cleaned it. It worked good for a while but when ever i got on the highway for longer then 15mins at around 100-120km/h if i ease off the throttle (i.e. coming down a hill) the check engine light will start flashing and then go solid. after a while it will disappear but then come on again. It will stay on for a couple days then go away. It has never done this while driving in town only on the highway. I don't notice any loss in power but it will drink a lot more gas and get terrible fuel economy until it goes away. Also about a month later it through a code for the MAF sensor which was count to high so i replaced that as well. What can it be?

PLEASE HELP!!!!
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby griff364 » May 11 2013, 3:01am

See if this will help you...

K&N intake, LT Headers, 3" exhaust, ARP Headstuds, COMP Cam, Upgraded rocker arm bearings, pushrods, and valve springs, AFM deleted, VVT deleted, LS7 Lifters, Tuned
Eaton SVT root supercharger @ 10 lbs
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby ASTE25 » May 11 2013, 3:06am

^^^Good information, but damn that guy is annoying!
Jordan
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby griff364 » May 11 2013, 3:10am

very much so!!
K&N intake, LT Headers, 3" exhaust, ARP Headstuds, COMP Cam, Upgraded rocker arm bearings, pushrods, and valve springs, AFM deleted, VVT deleted, LS7 Lifters, Tuned
Eaton SVT root supercharger @ 10 lbs
griff364
Combustion on 2 pistons [L2]
Combustion on 2 pistons [L2]
Posts: 229
Topics: 21
Images: 5
Joined: Feb 14 2013, 11:03pm
Years of membership: 1 year of membership
Location: San Diego
Year: 2011
Make/Model: GMC Sierra
Extra Info: 4x4 Flex Fuel
Group Membership:
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Servicemen

Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby mxz600rr [OP] » May 11 2013, 4:01am

Intake gasket was just done so i don't think it's that, my next tests will be fuel pressure and fuel pump. Why would it only be at highway speeds? Also ill do a battery and alternator test.
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby ASTE25 » May 11 2013, 4:28am

Check the fuel pressure and do a fuel pump volume check as well. It could also be a fuel pressure regulator if the pump is ok. One readon it could only miss at higher speed is due to fuel starvation due to a bad fuel pump of fuel pressure regulator.
Jordan
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Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
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Joined: Jan 03 2011, 6:37am
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby griff364 » May 11 2013, 4:41am

mxz600rr wrote:Intake gasket was just done so i don't think it's that, my next tests will be fuel pressure and fuel pump. Why would it only be at highway speeds? Also ill do a battery and alternator test.


keep us posted!
K&N intake, LT Headers, 3" exhaust, ARP Headstuds, COMP Cam, Upgraded rocker arm bearings, pushrods, and valve springs, AFM deleted, VVT deleted, LS7 Lifters, Tuned
Eaton SVT root supercharger @ 10 lbs
griff364
Combustion on 2 pistons [L2]
Combustion on 2 pistons [L2]
Posts: 229
Topics: 21
Images: 5
Joined: Feb 14 2013, 11:03pm
Years of membership: 1 year of membership
Location: San Diego
Year: 2011
Make/Model: GMC Sierra
Extra Info: 4x4 Flex Fuel
Group Membership:
How-to Authors
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Servicemen

Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby mxz600rr [OP] » May 12 2013, 5:01pm

So did a full electrical test and everything's fine, I filled up gas in the states and now the lights flashing in town now but only when the truck sits for more then a few hours, and it will come on about 3-5 minutes into my drive. Then it goes away. My last option is the fuel system :( I think I'm going to drop the tank change the fuel pump and clean out the tank.
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Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby griff364 » May 13 2013, 3:45am

I may have read over it, but have you tried the fuel filter?
K&N intake, LT Headers, 3" exhaust, ARP Headstuds, COMP Cam, Upgraded rocker arm bearings, pushrods, and valve springs, AFM deleted, VVT deleted, LS7 Lifters, Tuned
Eaton SVT root supercharger @ 10 lbs
griff364
Combustion on 2 pistons [L2]
Combustion on 2 pistons [L2]
Posts: 229
Topics: 21
Images: 5
Joined: Feb 14 2013, 11:03pm
Years of membership: 1 year of membership
Location: San Diego
Year: 2011
Make/Model: GMC Sierra
Extra Info: 4x4 Flex Fuel
Group Membership:
How-to Authors
Registered users
Servicemen

Re: 2004 Silverado 1500 5.3 Random Misfire HELP!!!!

Postby griff364 » May 13 2013, 3:48am

Nevermind... Just saw this blog.php?u=352&b=243
K&N intake, LT Headers, 3" exhaust, ARP Headstuds, COMP Cam, Upgraded rocker arm bearings, pushrods, and valve springs, AFM deleted, VVT deleted, LS7 Lifters, Tuned
Eaton SVT root supercharger @ 10 lbs
griff364
Combustion on 2 pistons [L2]
Combustion on 2 pistons [L2]
Posts: 229
Topics: 21
Images: 5
Joined: Feb 14 2013, 11:03pm
Years of membership: 1 year of membership
Location: San Diego
Year: 2011
Make/Model: GMC Sierra
Extra Info: 4x4 Flex Fuel
Group Membership:
How-to Authors
Registered users
Servicemen

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