White smoke when starting - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-01-2006, 06:24 PM   #1
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Default White smoke when starting

I have a wierd problem and I do not know where to tackle it first.

Every once in a while when I start my car, there a large cloud of white smoke from the exhaust. But I cannot recreate it (i.e, it happens on a cold start in the morning one day, but happens after running errands 3 days later). I have already done the UIM/LIM repair and the oil & plugs have been changed. The only thing I have done was put some SeaFoam in the gas (2 tanks ago) to clean out the fuel system.

Should I be worried that there is a larger problem or do you think it'* the SeaFoam?
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Old 08-02-2006, 10:11 AM   #2
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When did it start doing it? Before or after you put the Seafoam in?

How long ago did you do the UIM & LIM gasket fixes?

Are you using any coolant?
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Old 08-02-2006, 10:40 AM   #3
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What you are describing sounds like a small leak into a cylinder. White smoke is usually coolant. The cause could be a cracked head, bad gasket, or bad UIM. Get your nose near the exhaust in the morning and smell the smoke that comes out. If it is coolant, you should be able to tell. Another possiblility, is that you may be sucking transmission fluid into the intake manifold through a failed vacuum modulator. That won't smell like coolant.

Pull the spark plugs and carefully examine them. If one plug is noticeably cleaner than the others, that suggests coolant leaking into that cylinder.

If coolant is the problem, as Lash mentioned, you should notice a drop in the coolant level. When the engine is cold, check the level of coolant in the radiator as well as the overflow bottle.

I wouldn't think that Sea Foam in the gas would cause the problem.
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Old 08-02-2006, 01:31 PM   #4
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I can't remember if it was happening before the SeaFoam so it'* hard to pinpoint. The UIM/LIM gaskets were replaced about 4-6 weeks ago (guessing). I haven't looked at my coolant lately, but I think the level is OK. I can check that shortly.

I actually just changed the plugs and wires this past weekend. I should pull them back out of the garbage to check them out again. They were dirty, but I didn't recall seeing any coolant on them. I can post pics for further review.

Is there a way to verify if I have a bad vacuum modulator? A sound, error code, something? How can I tell if it'* a faulty UIM?

Thanks
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Old 08-02-2006, 03:32 PM   #5
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Just looked at my coolant at lunch and the level is fine. However I looked at my tranny fluid and it was a bit high. I'll try draining it a bit to see if that helps.
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Old 08-02-2006, 04:17 PM   #6
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A plug running in a cylinder that has a small coolant leak will look cleaner than the others, not necessarily wet with coolant. Pull the vacuum line to the modulator and see if there is evidence of transmission fluid in it. When the diaphragm fails, trans fluid can get sucked into the intake manifold through that line. No easy way to tell if you have a UIM failure without disassembly. But if your coolant level is steady, no worries for a coolant leak. Gotta look elsewhere. Maybe oil getting into a cylinder.

Again, smell the exhaust when it is smoking - that will tell you what the fluid is.
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Old 08-02-2006, 04:50 PM   #7
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Yeah, I recall all the plugs were dirty. None that were extremely clean. 2 questions though, 1, where is the modulator? and 2, where is the vacuum line for it?
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Old 08-02-2006, 06:42 PM   #8
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Quote:
Originally Posted by chzhead
Yeah, I recall all the plugs were dirty. None that were extremely clean. 2 questions though, 1, where is the modulator? and 2, where is the vacuum line for it?
The Vac line is on the TB, and will run down to the front of the trans below the wire connector

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Old 08-02-2006, 07:32 PM   #9
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If your weather in the morning is fairly chilly, it could be as simple as a cold morning air(more dense), and the combination of a cold engine, not hot enough to burn fuel efficiently, and just unburnt fuel coming out the pipes. Or possibly leaky injectors throughout the night.
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Old 08-03-2006, 03:03 PM   #10
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See, that'* the thing. It doesn't happen every morning.

Here'* the pics of my plugs.....
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About average with 125,000 miles, right?
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