Exhaust smoke: rings, head gasket(s), or valve seals?

[MHayes]

So I've posted this on ls1tech with little success...figure I'll pick your guys' brains for any info/suggestions you might have.

I've got a 96 lt1 trans am w/ 105k miles on it. It smokes at idle after being warmed up. It does not smoke on start up and does not smoke while driving. The smoke looks like coolant (there's definitely excessive moisture in it). However it smokes like bad valve seals sans the smoking on start up..and it's more a white-ish smoke. Here's where it gets interesting - the motor uses oil whether through the many small leaks I'm tired of chasing or possibly through bad rings? It does not use coolant and both the coolant and oil look good.

One thing I should note is I would notice, during the winter at JMU, there would be a white/yellow buildup in the oil fill tube. The car does not run hot and there are no SES codes. I had a mechanic look at it (literally made his judgement after seeing the car idle for <30 seconds) over a year ago and he said it was bad rings (motor still has good compression...at least according to the gauge).


I'm going to pull the plugs tomorrow and see how they look...that being said I know the car runs rich due to a poor mail-order tune. Honestly, I'm lost here....I want to sell the car and move on to something European.

[D_Eclipse9916]

Personally doesnt sound like rings to me, bad rings typically smoke on startup and get less as the car warms up. Do a leakdown test, compression test rarely does a good enough job.

If youve got an sort of milkshake, indicates oil and coolant are mixing. But from what it sounds like that white/yellow build up is just condensation during the winter by not driving the car long enough when you drive it. That stuff is common and goes away if you run your car long enough for the engine to fully heat up.

Can you smell the coolant? I feel like it would be fairly obvious to tell from that.

Good luck, and if your getitng rid of the lt1 let me know , but I hope you have good luck with it. Losing motors sucks (trust me I know).

[Steve85]

If it's rings the smoke will pour out when you accelerate hard. (note every 80's Caravan on the road leaving a stop light) Without the smoke at startup that also makes me lean away from valve seals. At idle, you have the highest vacuum, so suction on the PCV is greatest. This would not be the first time an engine sucked excessive oil from the PCV valve. Pop it off and if you can, look in the tube and see if there is oil in it. There will of course be a film, I'm talking about liquid oil that could very well be dripped out of the tube.

let us know what the plugs look like. It should be pretty obvious if you're getting a good bit of oil in there.

DJ is right if it was coolant that smell is usually pretty identifiable. Are you sure it doesn't have a blue tint as compared to the white exhaust you see from cars on a cold day?

[ScottyB]

does it make good power? maybe it's a clogged cat since it sounds like it smokes more as it gets hotter.

[ViPER1313]

Are you sure the smoke is coming from the exhaust? Maybe you have an oil leak that's dropping onto the exhaust and burning off?

[NTIman]

I wouldn't go by the oil fill tube, A lot of time condensation builds up inside the engine during cold months and ends up doing that to the tube/oil cap. Almost every Toyota truck does it, and I've never seen one with a blown head gasket.

I'd do a leakdown test since its fairly easy to do.

Other than that it's kind of hard to tell, since you know it runs rich, which could possibly make the engine smoke (though white smoke would be odd). I've always been told to fix the obvious stuff first.