Rough idle upon starting engine

Have a 2002 Silverado 4.3, upon starting the engine runs rough, feels like theres not enough gas to keep engine running. Check engine light comes on and once the engine warms up the engine idle smoothes out and of course before I can get the code read.... the check engine light goes out. Any Ideas?

Sounds like you might have a vacuum leak.

If you can get codes scanned they will probably be codes 171 and 174
left and right banks too lean.

Check all vacuum lines and connections.

If lines and connections are ok then check the intake manifold seam by spraying some starting fluid around the seam where the intake manifold
is bolted to top of engine.

Do this while the engine is cold because when engine warms up the manifold seals itself due to expansion.

That's why the engine runs ok after it warms up.

If the manifold is leaking and you spray starting fluid around the manifold seam the engine will stop missing and smooth right out.

My wild quess is the manifold gasket needs replaced.

About $215 @ chevy service dept.

Hope this helps, Bubba

Have a 2002 Silverado 4.3, upon starting the engine runs rough, feels like theres not enough gas to keep engine running. Check engine light comes on and once the engine warms up the engine idle smoothes out and of course before I can get the code read.... the check engine light goes out. Any Ideas?


Turned out to be the computer. After the new computer was installed, it picked up all sorts of codes and the service technician had quite a day fixing them. The engine starts right up now and the transmission seems to shift smoother now also. And one big plus is the increased mpg. Whoopeeee!