blue smoke and slight sputter

[HeWhoKillz]

When I start my car when it hasn't been drivin in a while, it makes a small sputter for a few seconds. Its not really missing out. When i give it gas blue smoke comes out the tail pipe. Could it be a head gasket? Or a spark plug not firing right? Or is it something else?

[shorod]

You left off some key information like what car and what engine.

If you have a Chrysler product with a 3.0L V6, or an '80's GM with 2.8L V6, it's probably valve seals or valve guides. Actually, any engine that has blue exhaust after start-up following a prolonged "rest" is a common symptom of leaking valve stem seals. On the engines mentioned above, it just happens to be pretty common.

-Rod

[HeWhoKillz]

Originally Posted by shorod

You left off some key information like what car and what engine.

If you have a Chrysler product with a 3.0L V6, or an '80's GM with 2.8L V6, it's probably valve seals or valve guides. Actually, any engine that has blue exhaust after start-up following a prolonged "rest" is a common symptom of leaking valve stem seals. On the engines mentioned above, it just happens to be pretty common.

-Rod

Sorry, its a nissan sentra, 1993, 1.6. Is there anyway to test this theory?

[vgames33]

My '93 does that. It is hard to start, makes a blue puff at startup, and then runs fine after all the oil is burned off. I'm not sure how to test the seals, other tan an inspection.

[shorod]

Other than taking the top end apart and inspecting the valve seals to see if they are hard and brittle, I'm not sure there's a way. What you describe is a pretty telltale sign for bad valve stem seals. When the engine is shut off, there will be pooled oil on the valve stem seal. If the seal is damaged and not sealing well, it will allow this pooled oil to seep past it and puddle either on the valve or on the top of the piston. When you first start the car, it is trying to burn off the oil making it slightly hard to start, but once it burns off the oil (blue exhaust) the speed that the valves open and close as well as the lack of pooling means it will run fine and it won't be apparent that any oil is being burnt.

-Rod

[HeWhoKillz]

Originally Posted by shorod

Other than taking the top end apart and inspecting the valve seals to see if they are hard and brittle, I'm not sure there's a way. What you describe is a pretty telltale sign for bad valve stem seals. When the engine is shut off, there will be pooled oil on the valve stem seal. If the seal is damaged and not sealing well, it will allow this pooled oil to seep past it and puddle either on the valve or on the top of the piston. When you first start the car, it is trying to burn off the oil making it slightly hard to start, but once it burns off the oil (blue exhaust) the speed that the valves open and close as well as the lack of pooling means it will run fine and it won't be apparent that any oil is being burnt.

-Rod

So to correct this, does one just take the head apart and replace the seals or would it be best just to get a new head?

[shorod]

That's your call, but new seals would likely fix the problem. You might search the Nissan Sentra forum to see if this is a common issue with a know fix (revised part number seals, or guides dropping into the head). They may also have a post explaining what's involved in the repair. Maybe you won't even need to remove the head to replace them.

-Rod

[vgames33]

Check nissanforums.com. You can usually find a free service manual for download for most OBD1 Nissans there.