A few days ago my truck threw a “service engine soon” light. I checked it and it was a bank 1 and 2 lean code. I cleared it. Truck ran fine since. Today I start it up and it stumbles around pretty badly at idle, almost stalls. After a few min down the road and it warmed up some, it seemed ok.
Has about 90k on it, and a aftermarket intake thats been on it for quite a while now. I have a feeling this problem isn’t going to just go away, what should I check for? Can bad o2 sensors cause this? Seems odd that both would crap out at once. Seems like it would be something intake related since bank1 and 2 threw the code.
a dirty/broken IAC valve can cause that to happen… does the light come on at idle?
or like jeff said, i think a leak after the mas air can cause those codes.
Well the CEL hasn’t come on since. Its run fine all afternoon, but I know when I start it tomorrow morning its going to do this again. I guess I’ll try to clean the MAF and IAC valve and make sure everythings tight.
I just dont want to start throwing money around at this truck if I dont have to. Im looking to sell it or trade it in shortly, but I want to make sure its fixed and fixed right before I do.
This PI was superseded to update parts information.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.
Oh man, hopefully thats not it cause its damn cold out to be pissing with all that. Thanks for the reply, if I can’t sort this out I guess the intake gaskets are next up.