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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.
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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.