Warped Intake? (sucking Fresh Air...running Lean...check Engine Light)

raisedinal · March 19, 2007

I had Check engine Light come on and it was labeled as 02 Sensor by local parts store. because of the number of 02 sensors and cost I took for Diagnostic eval at a local, non-dealer reputible (I think) mechanic to narrow which one. The mechanic read the codes but almost instantly said that it wasn't the O2 sensor but it was a gasket "Above the plenum" where the intake warps and it sucks fresh air and leans out the mixture sending off the O2 sensor light! He stated that this was common on these vehicles around roughly 100K miles (mine 97K). and that it required new intake and obviously gaskets as well. He said it was listed as 5-6Hrs on the books.

as anyone heard of this? is it common? I trust myself in gasket/intake replacement in this department as long as GM special tools aren't required.

If it is an intake that needs replacement...I know in the past aftermarket parts can sometimes be cheaper than OEM is this aceptible if it was the only upgrade done to the engine or would others be required?

I am just wondering b/c I have been googling and searching forums for a few hours now with no mention of this problem?

Please help!

Thank you

Justin T.

Norseman · March 19, 2007

I had Check engine Light come on and it was labeled as 02 Sensor by local parts store. because of the number of 02 sensors and cost I took for Diagnostic eval at a local, non-dealer reputible (I think) mechanic to narrow which one. The mechanic read the codes but almost instantly said that it wasn't the O2 sensor but it was a gasket "Above the plenum" where the intake warps and it sucks fresh air and leans out the mixture sending off the O2 sensor light! He stated that this was common on these vehicles around roughly 100K miles (mine 97K). and that it required new intake and obviously gaskets as well. He said it was listed as 5-6Hrs on the books.

as anyone heard of this? is it common? I trust myself in gasket/intake replacement in this department as long as GM special tools aren't required.

If it is an intake that needs replacement...I know in the past aftermarket parts can sometimes be cheaper than OEM is this aceptible if it was the only upgrade done to the engine or would others be required?

I am just wondering b/c I have been googling and searching forums for a few hours now with no mention of this problem?

Please help!

Thank you

Justin T.

It's possible (not common) but, the only way to really tell if the intake manifold is warped is to remove it. Then locate a straight edge across the intake manifold cylinder head deck surface. Position the straight edge across a minimum of two runner port openings. Insert a feeler gauge between the intake manifold and the straight edge. A intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area is warped and it should be replaced.

Yukon04 · March 19, 2007

Usually, to find intake type leaks, spray some ether (or equivalent) around the base where the two parts meet. Continue spraying around the joint until there is a change in the idle. This will tell you if there is an air leak.

Norseman · March 19, 2007

Usually, to find intake type leaks, spray some ether (or equivalent) around the base where the two parts meet. Continue spraying around the joint until there is a change in the idle. This will tell you if there is an air leak.

That is true it will tell you if there is a leak but, it WILL NOT tell you if the intake is warped. FYI.

Z71Rider · March 20, 2007

Isn't that intake made of plastic? And, it is, how can it really warp? So assuming it is warped (or whatever), and a new gasket won't fix it. Since this place is not under much vacuum (or delta pressure), what would be wrong with simply using a sealant, like a silicone, and fix the leak that way?

My last resort would be a new OEM that would have the same design flaw that would probably do the same thing later.

bossier62guy · March 20, 2007

Do you recall the fault codes? Intake gaskets are a common problem on these engines at least for the 02 models. You're obviously going to have to remove the manifold to replace the gaskets so check it when it's off. I haven't heard of any issues of them warping though.

TBLAZER · March 20, 2007

I had Check engine Light come on and it was labeled as 02 Sensor by local parts store. because of the number of 02 sensors and cost I took for Diagnostic eval at a local, non-dealer reputible (I think) mechanic to narrow which one. The mechanic read the codes but almost instantly said that it wasn't the O2 sensor but it was a gasket "Above the plenum" where the intake warps and it sucks fresh air and leans out the mixture sending off the O2 sensor light! He stated that this was common on these vehicles around roughly 100K miles (mine 97K). and that it required new intake and obviously gaskets as well. He said it was listed as 5-6Hrs on the books.

as anyone heard of this? is it common? I trust myself in gasket/intake replacement in this department as long as GM special tools aren't required.

If it is an intake that needs replacement...I know in the past aftermarket parts can sometimes be cheaper than OEM is this aceptible if it was the only upgrade done to the engine or would others be required?

I am just wondering b/c I have been googling and searching forums for a few hours now with no mention of this problem?

Please help!

Thank you

Justin T.

Here is a document on Gen 3 intake leaks.

Document ID# 1899786

2002 Chevrolet Chevy C Silverado - 2WD

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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

Models: 2002-2005 Cadillac Escalade

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

1999-2005 GMC Savana, Sierra, Yukon

2003-2005 Hummer H2

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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.