Skipping Hummer h2

[HUMTECH]

If you have an intake(vacuum) leak it will almost always set a lean mixture code and will turn on the ses light. Need a scan tool to force it into closed loop operation and monitor fuel trim levels while spraying air intake cleaner around the intake gaskets with the engine cold, if the fuel trim levels change dramatically the intake is leaking. Dont think this is your issue though. I will put some thought into it and see what i can find.

[HUMTECH]

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=1899786&from=sm#ss1-1899786">Condition/Concern:

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

1. <LI type=1>A cold rough idle that diminishes as the engine warms up. <LI type=1>Possible DTCS P0171, P0174, or P0300.
2. Random misfires at idle.

<A href="http://gsi.xw.gm.com/si/showDoc.do?docSyskey=1899786&from=sm#ss2-1899786">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.

1. <LI type=1>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.
2. 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.