New to the forum. Have had rough cold idle off and on for a year (comes for a month or so and goes for a month or so). CEL is on solidly and getting 0171 and 0174 lean mixture codes. 85K miles. Sounds pretty much like the intake manifold gasket(s) need to be replaced. Is this a DIY project for someone with good mechanical skills, no experience working on engines, and an average set of tools?

 

Definitely sounds like intake gaskets. The 5.3 is one of the easiest intakes around. In a shop it only takes about a hour for start to finish. You will need a special tool the remove the fuel line from the rail but the are less than $20.00 probably closer $10. The gaskets have been updated I recommend getting the from the dealer. The new gaskets are green the old design is orange. It is highly recommended that you torque the intake back down, plastic intake, plastic and rubber gaskets.

 

Thanks MD. Very much appreciated. Only thing that concerns me about the job is that EVAP tube that goes way back behind the head. That thing looks to have to be disconnected in order to get the manifold off, and you are totally blind back there. Also, the official GM instructions look to have you take all kinds of stuff off of the manifold that are not necessary to get it off the engine. Still leaning toward letting a pro do this one...

 

Interestingly, took the manifold cover off to have a look around and found the EVAP purge solonoid module's bolt about to come out, and the thing very loose in its seat. Since that thing plugs right into the intake manifold, could this be causing my vacuum leak???

 

Is it a through hole or does it have a bottom?

 

Looking at an EVAP system schematic, looks like the solonoid is plugged right into the vacuum. Odd thing is that I checked the torque and it's right on 10NM, but the solonoid is loose and wiggles around a lot.

 

Well, swapped the old orange gaskets for new teal ones from the dealer and the thing has never started more quickly and run more smoothly. Thanks for the help.