I have a 2003 5.0 Express that has 61,000 miles. When I start it up, a good cloud of light gray smoke comes out of the exhaust and if I give it gas, it becomes darker. Can anyone tell me what causes this and what do I need to do to correct? I want to change the PVC first and see if this fixes the problem. Where is the PVC exactly and do I need to remove the inside engine cover to access it. I change my oil every 3,000, usually at the Chevy dealer, if that matters. Thanks in advance.

 

I think its more than just a PCV valve. I think a ring set or valve seal(s) is blown, Id start with a compression test on all cylinders when its cold.

 

Mike, its very possible that the PCV is regurgitating oil, which is then sucked into the engine. I wouldn't rule out that possibility at all.

It is possible that you have a head gasket or piston ring failure.

 

Your right now that I think about it, It would be ingested into the intake, my bad

Your PCV should be on the drivers side valve cover on the back.

5.0 you mean a 6.0 or 5.3? There is no 5.0 in 2003 for Chevy, is it the 1500 or the 3500? I tried to look up your PCV valve for you.

 

Sorry, it's a 5.3, 1500.

 

No prob, yea your PCV is on the drivers side valve cover in back, its hidden in the foam hose that plugs onto the valve cover

 

Pull it out and put your finger over the valve and make sure there is vaccuum if not replace it! With engine off shake the valve and listen for a rattle if there is no rattle replace it!

 

I'd be checking for a rich condition....could be something as simple as fouled plugs not burning all the fuel when cold, or patrially plugged injectors. When was the last tune-up?

 

"Give gas..." you're Dutch, arent you?

Check your plugs. If the grey cloud is oil or fuel, then you should see it on your plugs as well.
If its oil, then you have a problem. (rubber thingies that keep oil from seeping in your combustion chamber... but dont ask me the english name for that. )
If its gasoline, then you should smell it when you stand inside the smoke. "I love the smell of napalm in the morning."

Gasoline problem can be caused by various things. Wrong combustion timing, wrong spark plugs, wrong kind of fuel, too much fuel injection, broken spark plug, one of the spark wire thingies thats malfunctioning... You can all check that by just getting your spark plugs out and controling them.
Wrong combustion timing : 1 or more of the plugs will show greasy substance.
Wrong spark plug : it'll be greased up from top to bottom. (elektrode and insulator)
broken spark plug : well... it'll be broken...
spark wire issue : 1 spark will have grease, all others will be just fine.

Since it becomes darker only when you "give gas" , I think its gasoline and not oil. Only time (and probably an expensive car repair man) will tell.

We should get points for correct answers :-D