My wife was driving home and engine light started to flash and she said that it seemed like it was smoking from the back. I got home and checked it> started and ran fine for me it did have code po300 and the tail pipe seemed a little black. cleared code and it's been running in driveway for 30 min now with no codes engine temp seems a little low about 185 after running for the 30 min it is cold here about -6 any ideas?

 

Just ran a Google search for Chevrolet CEL code PO300 (Google is your friend!)

The first hit was for a who has some valid points (despite using a Toyota for his example). Check the same things on your vehicle.

If it's a vacuum leak, check the vacuum hoses and the intake manifold/plenium seal for leaks. I hear that the intake manifold gaskets can be the culprit. Before going for something like that, rule out all the smaller, easier, and cheaper possibilities.

 

ya I did google it just seemed like there was so many possibilities on a google search was hoping that some had similar problem and I could narrow it down.

Funny thing I cleared the code and she drove it about 45 miles today with out issues. I know that the problem is going to come back.