I have a 2004 Tahoe with this problem. It started with the trucks rpm going up and down to a point when we would be at a stop light the truck would stall out. After replacing the intake gasket and new throttle body that no longer happens and the check engine light was off. Recently however, the engine light is back on with a black substance coming from exhaust pipe staining the concrete when we turn it on. Also the first 15 minutes when we turn it on it runs like its going to stall but the rpm stays pretty consistent. I am fearing the worst. I read somewhere this could be the exhaust gasket. Any suggestions would be greatly appreciated.

 

any codes?

 

Just the check engine light and I havent taken it to a mechanic yet to have them check the computer.

 

Most autoparts stores like Autozone will read you codes for free.

 

if its black from running rich, get it checked out now before the convertors are damaged.