Help with a 2003 Silverado LT Z71
April 1st, 2010 | 7:41 AM
#11
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Professional Mechanic
Professional Mechanic
Joined: Nov 2008
Posts: 2,950
Likes: 4
From: Bowie, MD
O2 sensor low voltage means that they are reading a lean fuel mixture low voltage is lean high voltage is rich. This does not mean the o2 sensors are bad. What is the freeze frame engine temperature for the codes?
April 1st, 2010 | 8:59 PM
#13
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Professional Mechanic
Professional Mechanic
Joined: Nov 2008
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From: Bowie, MD
I am leaning towards bad intake gaskets. Does it run worse when it is cold? GM has actually updated the gaskets because of a problem. You really need to check the fuel pressure first though to make sure it is not a low pressure problem.
Date: June 24, 2005
TECHNICAL
Subject:
Flexible Fuel (RPO L59) Rough Idle, Misfire, MIL DTC P0300
(Install Intake Manifold Gaskets With Teal Green Gasket Material)
Models:
2002-2004 Chevrolet Silverado, Suburban, Tahoe
2002-2004 GMC Sierra, Yukon, Yukon XL
with 5.3L Engine and Flexible Fuel (VIN Z - RPO L59)
This bulletin may apply to the following engines using regular fuel: 4.8L, 5.3L, 6.0L (VINs V, T, P, U, N - RPOs LR4, LM7, LM4, LQ4, LQ9).
Supercede:
This bulletin is being revised to add additional diagnostic information. Please discard Corporate Bulletin Number 05-06-04-029 (Section 06 - Engine/Propulsion System).
Important :Always begin your diagnosis with the Diagnostic System Check - Engine Controls (SI Document ID # 1289827) for any MIL or driveability concern. The Diagnostic System Check directs you to the next logical step in your diagnosis. Follow the instructions in this bulletin should the rough idle, misfire, or DTC P0300 diagnostic procedure point to an air leak in the intake manifold gasket. Following the published diagnostic procedures will improve diagnostic accuracy and support our fix it right the first time approach.
Condition
Some customers may comment that the vehicle may have a rough idle, misfires and/or a MIL illuminated with a stored DTC P0300.
Cause
The L59 engine is calibrated for ethanol fuel (E85). Due to the low volatility of ethanol, the PCM provides higher fuel flow through the injector, which may pool on the upper manifold to head gasket material. Overtime (usually 12 months and longer), the gasket material may degrade resulting in an unmetered air leak.
Correction
Replace the upper intake manifold gaskets with the teal green gasket material, P/N 89017589.
Important
o not replace the upper intake manifold gaskets with the original orange gasket material, P/N 17113557.
Inspect Intake Manifold to Cylinder head Deck for Warpage
Important :The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced." Intake warpage is measured at the gasket sealing surfaces and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
Important :Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary intake manifold replacements.
1. Locate a straight edge across the intake manifold cylinder head deck surface. Position the straight edge across two runner port openings.
2. Insert a feeler gauge between the intake manifold and the straight edge. An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area is warped and should be replaced. Do not replace intake manifolds with warpage that measures less than 3 mm (0.118 in) over a 200 mm (7.87 in).
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
Date: June 24, 2005
TECHNICAL
Subject:
Flexible Fuel (RPO L59) Rough Idle, Misfire, MIL DTC P0300
(Install Intake Manifold Gaskets With Teal Green Gasket Material)
Models:
2002-2004 Chevrolet Silverado, Suburban, Tahoe
2002-2004 GMC Sierra, Yukon, Yukon XL
with 5.3L Engine and Flexible Fuel (VIN Z - RPO L59)
This bulletin may apply to the following engines using regular fuel: 4.8L, 5.3L, 6.0L (VINs V, T, P, U, N - RPOs LR4, LM7, LM4, LQ4, LQ9).
Supercede:
This bulletin is being revised to add additional diagnostic information. Please discard Corporate Bulletin Number 05-06-04-029 (Section 06 - Engine/Propulsion System).
Important :Always begin your diagnosis with the Diagnostic System Check - Engine Controls (SI Document ID # 1289827) for any MIL or driveability concern. The Diagnostic System Check directs you to the next logical step in your diagnosis. Follow the instructions in this bulletin should the rough idle, misfire, or DTC P0300 diagnostic procedure point to an air leak in the intake manifold gasket. Following the published diagnostic procedures will improve diagnostic accuracy and support our fix it right the first time approach.
Condition
Some customers may comment that the vehicle may have a rough idle, misfires and/or a MIL illuminated with a stored DTC P0300.
Cause
The L59 engine is calibrated for ethanol fuel (E85). Due to the low volatility of ethanol, the PCM provides higher fuel flow through the injector, which may pool on the upper manifold to head gasket material. Overtime (usually 12 months and longer), the gasket material may degrade resulting in an unmetered air leak.
Correction
Replace the upper intake manifold gaskets with the teal green gasket material, P/N 89017589.
Important
o not replace the upper intake manifold gaskets with the original orange gasket material, P/N 17113557.Inspect Intake Manifold to Cylinder head Deck for Warpage
Important :The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced." Intake warpage is measured at the gasket sealing surfaces and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.
Important :Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary intake manifold replacements.
1. Locate a straight edge across the intake manifold cylinder head deck surface. Position the straight edge across two runner port openings.
2. Insert a feeler gauge between the intake manifold and the straight edge. An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area is warped and should be replaced. Do not replace intake manifolds with warpage that measures less than 3 mm (0.118 in) over a 200 mm (7.87 in).
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
September 19th, 2013 | 9:20 PM
#16
Super Moderator
Joined: May 2008
Posts: 2,474
Likes: 20
Hi Chvy2003man,
Welcome to the Chevy Forums.
I'm just going to mention it won't cost anything to
clean your MAF sensor, that little plate full of holes
right past your air filter, before your throttle body.
I'm assuming your air filter is clean?
Welcome to the Chevy Forums.
I'm just going to mention it won't cost anything to
clean your MAF sensor, that little plate full of holes
right past your air filter, before your throttle body.
I'm assuming your air filter is clean?
Last edited by therewolf; September 19th, 2013 at 9:29 PM.
September 19th, 2013 | 9:52 PM
#19
Administrator
Joined: Apr 2008
Posts: 7,573
Likes: 45
From: Austin, Texas
Hopefully pinging the thread again might get the OP to update the post of whether it did or didn't fix it...
Last edited by in2pro; September 19th, 2013 at 9:53 PM. Reason: corrected speeling :)