95 Audi 90 Quattro Oil smoke in exhaust.

I have a 1995 Audi 90 Quattro with 165,000 miles.
This morning I noticed a small cloud of smoke that I left at an intersection when I pulled out. When I got to work I opened the door and
pressed on the gas and watched a faint (not opaque) cloud of oil (not water) smoke form behind the car. This was more than a little disturbing.
From what I know, this could be coming from a head gasket, piston rings or valves? How might I decide which is the cause?
Of course, after coming home from work, I could not reproduce the symptoms. Sticky piston ring?
Gene
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I think I've learned another detail about this. I saw the same puff of smoke at the same intersection this morning. I realized that this stop sign is at the bottom of a hill that I coast down in gear using the engine to gently limit my decent. It would seem to me that, in this condition, I may be sucking oil past rings or valves into the combustion chamber without buning it while I coast down the hill, then it burns under accelleration. It's been suggested to me that these engines don't tend to wear piston rings or cylinder walls much at all. So, I guess I'm looking at valve guides?
Gene

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rings
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Gene, You might try a "leakdown test" - I believe that may tell you if the leak is through the rings (= "blow-by"). In an intake vacuum condition - throttle body closed, engine winding away to slow the car, I would expect it to the valve guides as well. Cheers! Steve Sears 1987 Audi 5kTQ - valve guides replaced with head gasket....one of those "while you're at it" things. 1980 Audi 5k - goesn't burn oil so much as leak....darn cork-shrinking synthetic oil. 1962 and '64 Auto Union DKW Junior deLuxes - burns 1 litre of oil every 40 litres of gas....even when it was new. (SPAM Blocker NOTE: Remove SHOES to reply)

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Pulling the heads and replacing valve guides (and all the gaskets) seems to have cleared this all up.
A point of interest: All 6 cylinder walls still have visible original factory cross-hatching. The engine has 180,000 miles on it! I expect I'll be driving this for a long time to come....unless I decide to get a 30V A4 some day.

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