Was'nt sure where to post this, but figured this may be a good spot.

I have an 03 Suburban 5.3 w/ 65,000 miles thats giving me lean condition codes for both banks.

I have cleaned the MAF and since its both banks I assume O2s are not the issue. The main symptom is that every once in a while at a dead stop idle in gear it will drop way down in idle and rpms will bump around like a small misfire. It hasnt ever died, just really stumbled low. As soon as I touch the gas it smooths right out. All other drivability is great.

Not real sure what to look at and I dont want to just start throwing parts at it. Any advice on what items to take a look at?...Thanks!

 

Intake manifold gaskets. Common problem on trucks setting lean codes.

 

Interesting... is there a way to test for it or do I just have to dig in and swap them to find out? Thanks for pointing that out...

 

spray some brake or carb cleaner around the area while running and listen for engine speed to change. Just don't burn the vehicle down and use caution while doing so please.

 

well.......................... looks like its time to Rinse and Repeat

 

Gave that a shot, and it didnt really change the idle at all. I tried to get around all the ports too. Could it still be leaking even though I didnt get a change in rpms? What else should I look at? Fuel psi?...

 

It's best to spray it down when engine is cold because it's more likely to leak cold. When things heat up, the gaskets swell and don't leak as much. If you can monitor missfires while spraying it down, you may see missfires. Fuel trims will be lean at idle, but not as much off idle too.
I work at a GM dealership and have replaced many of these gaskets for leaks. There was a design change too. The newer GM gaskets have green sealing rings on them. They aren't cheap either. Good luck.