1999 5.3 liter silverado
 

I have been having a problem with my silverado and I was wondering if anyone could shed some light. When I first dtart my truck in the morning, it stumbles and misses really bad for the first minute or two and then smooths out and runs well. I have been getting an intermittent code saying bank one and two are lean. Fuel pressure is around 48psi at idle. could this be a fuel pressure regulator??
Thanks!

RE: 1999 5.3 liter silverado
 

sounds as if not getting enough fuel when cold. Needs to run rich at first till engine warms then adjust. I do not know which sensors could be bad as there are so many, but someone here will probably know.
Also welcome to the forum.

RE: 1999 5.3 liter silverado
 

Hello...I had a similar problem with my 2002,5.3L. Main problem was a weak battery...cold morning starting pulled the voltage down for a bit until it recharged. Ran fine the rest of the day even after letting it sit for hours at -20C.
I understand GM's have problems with their intake manifolds leaking as well, which causes the same problem. Pouring water on the Intake manifold while running rough will usually smooth out the idle...
Hope this is of some help.

Barry

RE: 1999 5.3 liter silverado
 

Yes, that would be the "fundamental" problem. The source of the problem is less obvious and possibly varied. The very first thing I would do is test the oxygen sensor. It costs virtually nothing but a little time and can provide some valuable information before you go throwing parts at it. Presumably, this model has a heated oxygen sensor - probably has at least 3 or 4 wires? If so, I would first be concerned that the heater on one of the O2 sensors isn't working properly. I've posted these links before, but here's how to test that O2 sensor if you're not familiar:

O2 Sensor Info/Testing
O2 Sensor Testing

If the O2 sensor tests out all right, then I'd start exploring options in the fuel and intake system.

RE: 1999 5.3 liter silverado
 

thanks for the replies. It was suggested to me to remove the IAC valve and check that it is clean and functioning properly. Where is the IAC located?