Question about 1990 Nissan 300ZX

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1990 300zx non-turbo coupe 5 speed

I don't know if this really works but ill try it

I have a 1990 300zx non-turbo that is blowing out white smoke (not blue)and something wet smells like gas out of the tail pipe. I need help on what to do to fix it.

Thank you

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  • Gary Queen
    Gary Queen May 11, 2010

    White smoke is an indication of water in the combustion chamber. Are you going through coolant?



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Old post but I would like to state that white smoke and white vapor are two different thing and blue smoke is sometimes so ligh it looks white but does act like heavy smoke. Evanescence of water vapor looks a lot like smoke but dissipates a lot quicker but in mass quantities can look like smoke (yes..I been dying to use that word ever since I heard of the band Evanescence lol). Transmission fluid can be sucked into the engine via a bad shift modulator both that has no bearing here (just FYI). In either case you would be fouling out spark plugs due to oil or water saturation and causing unburned fuel to be expelled.

Posted on Feb 17, 2009

  • Marco Avila
    Marco Avila Jun 03, 2010

    Hi, did my info help any? Did you ever find the cause?


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Garyq1970 is right - white smoke usually indicates burning coolant. How full is your radiator? You should see coolant right up at the top of the fins inside when you remove the cap. Take a look and see if a) you are low, and b) if the coolant looks sludgy or contaminated, brown in color. If it's low, top it off and monitor it over a week's driving and see if you have to refill it again. If it's contaminated and brown, you have a problem.

Usually when you're burning off coolant, it's because of a torn head gasket allowing coolant into the cylinders. If it's not contaminated, that means the tear is between a water galley and the cylinder. If it's browish looking, then it's a tear between a water galley, an oil galley, and the cylinder, and the coolant and oil are mixing as well as being burned off. Either way, it's a very involved repair, as the top of the engine has to be removed to fix the problem. This involves removal of the upper and lower intake manifolds, and the entire timing belt system (which, given the in-depth job that the timing belt is, you might as well replace it, its tensioner, and the water pump and thermostat as well, to save yourself the labor later on). It's not a job for the faint of heart or wallet.

You may not be looking at such a repair but if you can monitor the coolant for a week or so and reply afterward and let me know, I'll take it along from there (just send me a request on here).

Posted on Sep 08, 2008

  • Meng Lee
    Meng Lee Aug 15, 2013

    i have a 1990 300zx na and i replace the injector with 370cc which is the turbo injector then the engine wont start, so i send my icu in to upgrade to fun 370 cc injector. after the icu came back i plut it in and the first second i start the motor, theres white smoke coming out of the exhaust. sometimes it would stop but always come back. you guys know what went wrong. thanks



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