Bank 1 Lean Condition With Random Misfire 1-3-5-7

[mx_racer428]

i have a 2004 chevy silverado 1500 with 5.3 4x4. after i statred my truck up form filling up with gas and the engine light came on and started flashing witch you know is becasue its misfiring, took it to get the codes read and said lean bank one and random misfire.. hooked it up to a snapon scanner and was showing misfires on cylinder 1-3-5-7 but mostly 1 and 3. took plug 1 out and was black as ..... i refilled the truck two times now and one time was with 91 and some heat- fuel injecter cleaner. the last two times i have drove it the truck started to run normal. regular gas milage and everything. then i shut it off and started it again and light came back on and same prob. but cleard up again. started it this morning and the same problem. it idles rought and its running so ritch that there is suit coming out the pipes. i have good consistant fuel pressure. any and all info would be greatly appeciated!!

[bobcat5544]

It is most likely the intake manifold gasket.

 

Document ID# 1899786

2004 Chevrolet Chevy K Silverado - 4WD

--------------------------------------------------------------------------------

Subject: Cold Engine Idle Misfire Or DTCs P0171 P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake leak lean misfire miss P0171 P0174 P0300 power rough surge vacuum #PIP3232B - (02/07/2007)

 

Models: 2002-2005 Cadillac Escalade

1999-2005 Chevrolet Avalanche, Express, Silverado, Suburban, Tahoe, Trailblazer

1999-2005 GMC Savana, Sierra, Yukon

2003-2005 Hummer H2

--------------------------------------------------------------------------------

This PI was superseded to update parts information. Please discard PIP3232A.

--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

 

Condition/Concern:

99 through 05 GEN III truck engines may experience any of the following:

 

A cold rough idle that diminishes as the engine warms up.

Possible DTCS P0171, P0174, or P0300.

Random misfires at idle.

Recommendation/Instructions:

The intake gasket seals may be leaking around the intake ports, causing a lean condition. The intake gasket seals may leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also notice lower than normal MAF readings if the intake seals are leaking.

 

If leaking intake gasket seals are found, replace the intake gaskets. During the repair be sure to use the current GMSPO part number for replacement intake gaskets. The current GMSPO part number for intake gaskets will have a teal green intake gasket seal. The old version of the intake gaskets were orange in color. Use only the teal green colored gaskets for a repair.

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.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.