Maybe Head-gasket replacement?
 

hello everyone I was curious if anyone could help me out here, I have a 99' civic si and recently white smoke comes out of the exhaust but it's not constant. it only happens when I'm in first gear once I accelerate but it doesn't happen everytime I'm in first. from some research I'm guessing it might be a bad head gasket? also if it is that does anyone have a link or recommend anything particular? Thanks in advance.

welcome to the forum. before you do anything, have you ever overheated the engine? if not, are you loosing anti freeze and adding quite often, if not does the engine run rough, if not check your engine oil to see if the oil is increasing and turning cream in color, if not it may be condensation. also if you are adding oil to the engine, it may be burning oil through the rings or through the valve guides.

Head gasket failure has telltale signs
Also can best tested
Suggest looking at a few youtube videos on busted head gaskets before deciding what to do next

Oh, just remembered, sometimes, smoke could mean the rings ... well, whatever

thanks for the replys guys, appreciate it. just to be safe I changed oil and spark plugs yesterday because I'm not sure how long ago the last owner did that. but the problem still persists what I did notice today was I can trigger it by holding down the clutch and easing off until it almost stalls.

I would do pressure test on the Radiator with the engine warm not hot, remove the cap cold start the engine let it warm up with the cap off until the fan comes on. If there is crack or blown head gasket many times you will get compression coming out of the radiator. if not shut the car off then hook up the pressure tester and watch for leak down on the gauge. The reason for doing this warm is if there is a crack in the head gasket or head being warm will open it more then being cold. You might also do a compression test, remove all the plugs test each cylinder write the psi down move to he next one compare each. Check the anti-freeze for oil, check the oil for anti-freeze. Does the smoke smell like oil or does it smell sweet? If like oil as stated above could be valve seals or rings. If sweet smell it is anti=freeze. good luck and let us know!