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  1. #1

    Default white sulfur smelling smoke from under the hood

    Hello, I have a 97 Chevy Silverado 5.7 ...sometimes when I try to start it it just shudders and a white smoke comes from under the hood and then I can start it. Any ideas??? thanks in advance---Bryan

    Last edited by bniland; 04-23-2012 at 03:30 PM.

  2. #2


    Is this a manual transmission? I've only noticed smells like that when a clutch is burned or burning up. Sound like the friction disk may be sticking on the input shaft of the transmission and not fully releasing. This happens when the splines get worn and the disk doesn't move freely back and forth. Otherwise I have nothing.

  3. #3


    I always related the sulfer smell to the catalytic converter
    Please Tell Your Boobs To Quit Staring At My Eyes

  4. #4


    Dinosaur motor oil contains sulfur. This is likely where the smell is coming from, as in burned sulfur residue.
    1994 Chevy K2500 Silverado, 454 (modified), original owner.
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  5. #5
    Master Mechanic
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    Well my first guess is that some one was cooking clutch cookies, in low fat dinosaur Oil in their brand new Catalytic converter oven.....
    but then i thought about it and that would be to easy, we would see beer cans strewn all about......
    but seriously your description sounds to me like you have some back pressure problems from a bad or burt catalytic converter........

  6. #6


    Hi, Bryan:

    A catalytic converter (since it has been referenced twice in replies) has panels containing rare metal molecules that bind with certain pollutant compounds in engine exhaust, removing them from the exhaust. If it gets contaminated, it will begin to malfunction. Contamination occurs from the air/fuel ratio being incorrect or some other problem that dumps fuel into the exhaust, or possibly from a lot of oil blow by (from maybe even one or two leaky valve seals), or from repeated moisture accumulation.

    I have had a contaminated and plugged (this is a term of art when used with catalytic converters because exhaust still goes through it, just not as much) catalytic converter on my truck. If you have your converter beneath the cab like I do, then you will know whether you have this problem. Here's what you do, it is simple: drive your truck about 10-15 miles, then stop, pull up the carpet where the converter is below the floor, and try putting your hand on it. And first take a close look at the paint on the sheet metal. Does it look brown as in burned? When you get your hand close to the metal, does it feel as though it is as hot as a stove top burner that was just turned off? If yes, then you have a problem with your cat converter. I have read in some car forums that owners have reported the plugged converter getting "red hot" (there was such a thread in a Corvette forum and in a Ford forum).

    Mine got damaged because I had new aluminum heads (Edelbrock) put on my engine and they custom built the roller rocker assemblies and after all the work got done I drove it on a trip. It sucked 4 quarts of oil in about 2000 miles. Before it sucked maybe a half quart in that distance, if that. Turned out the valve seals on one or two cylinders were leaking badly. Unfortunately, because the warranty on the heads (Edelbrock put in the valve guides and seals) was expired, Edelbrock wouldn't lift a finger to help me out, so I had to pay a buncha money for not only repair of the valve seals (they replaced all of them to make sure), but I had to put in a new catalytic converter, and they are not cheap.

    I ended up replacing the exhaust from there back with a four inch system and muffler. Sounds real nice, but all this cost me dearly, all because of the oil going through the valve seals.

    However, I never smelled any sulfur burning. Never had any smoke either. But I have a 454.

  7. #7


    Ever been behind a car that the emissions were off spec? You get that sulfur smell from their exhaust. I to believe hat the catalytic may have some responsibility but the white smoke seems like a chemical burning , to create the white smoke. usually oil burns dark colored smoke. But it seems that the vehicle is not hot when you start it so the burning may be far fetched. Could wires be crossed and burning the covering off the wiring?

    Let us know what you find
    2010 Chevy Silverado Z71 ext cab.4x4
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  8. #8


    Something else that will cause this is cheap or bad gasoline. If your oxy sensor is sluggish, or going out, but doesn't yet throw a code, it will think the fuel ratio is too lean when if the catalytic converter is beginning to plug up badly and tell the computer to send more gas to the injectors. This is where bad or really cheap gas will smell like rotten eggs or sulphur and you'll get that brief white cloud of smoke. Not enough air in the ratio. This would be an upstream injector. The situation will only get worse. Check your oxygen sensors and cat converter.

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