I own a 1988 chevy 4x4 blazer 4.3L with a magnaflow muffler when I first Start the truck after sitting for a day or so smoke will come out of the tailpipe but after I rev the crap out of it the smoke goes away but comes back when the engine revs back down. Does anyone know what could be causing that? Thanks in advance for the help.

 

What color is the smoke?

White = burning coolant (not going to burn at startup though)
Blue = Burning oil
Black = rich on fuel

Keep in mind your truck is about 15 years old, and valve stem seals can leak some oil and burn it. They tend to leak less once warmed up as tolerances get a little tighther as things warm up.

 

Thank you, I just took the spark plugs out to see if any oil is in any of the cylinders I noticed there was not any oil on the spark plugs I talked to a mechanic the other day he said that it could just be needing an oil change.

 

Might be valve seals, just after the warranty went out on my 92 S-10 4.3 it started doing something like that, Chevy house replaced the vale seals, now has 160,000 plus and never has done it again.

They replace them with valve seals for a Chevy V8.

 

Thanks is there any way to check and see if it is the Valve Seals for sure? Thanks

 

I took mine to the Chevy house, they said that was the problem, they changed them, and all has been well ever since. OH, they replace the valve seals with seals from a V8, said if we put seals back in from the V6, both intake and exhaust, it would probably be doing the same thing shortly.

 

do a compression test. if you have low compression then you have a bigger problem then valve seals.

if your compression is good theirs a good chance its your valve seals.

you can get a compression test tool at pep-boys for like $30.

you said you checked a spark plug chances are you checked the wrong one most likely it is only one cylinder that is the problem.

 

I pulled all of the spark plugs and they seemed ok Just needed to be cleaned I cleaned the spark plugs and put them back in my truck.

 

You said it only does it when its been sitting for a day or so? Could just be condensation from sitting. Drive it for 15 min and if its still smoking then check compression etc. If its gone then its just condensation or weak valve seals. Valve seals isnt a really big deal if it just smokes on start up for a few min. Just keep a eye on the oil time to time. Mine has bad valve seals and i have to add maybe a pint of oil every 2 weeks.

 

UPDATE I changed my oil and put some oil smoke treatment in with my oil and it stopped the smoke that was coming from the oil.