Power loss and white smoke
auditude at gmail.com
Tue Apr 11 13:51:46 EDT 2006
I don't know what to say about the grunk noise, but I would suspect
the valve stem seals are the cause of the smoke on startup. I see
this in my 200q20v, and I may have even seen it with my CQ before. My
friends former CQ had the same issue.
As the car sits after being parked, the oil above the head seeps down
past the stem seals and rests on the back of the valves. Upon
startup, the valves open and this oil is dropped down into the
combustion chamber to be burned.
I would try some of the oil treatment stuff that is intended swell up
the seals that I think Bernie has suggested before for various things
as an alternative to replacing seals. I believe my friend tried the
Lubro-Moly or similar German brand in his former CQ and it helped a
bit. At least that way if it goes away you can rule out the smoke as
being related to the grunk noise.
I would think if oil was leaking past the turbo, it would be smokey
under boost more so than upon startup. I think driving hard might put
more oil above the head to leak into the chamber than normal driving
would, but if that's not correct I'm sure someone will correct me.
I wonder what that grunk noise is. Have you pulled codes? Perhaps
all the oil getting into the chamber is affecting the detonation
resistance. I know people go to lengths to prevent oil from being
recirculated around in the breather system unecessarily, so perhaps
the noise and smoke are indeed related.
Would you describe the power loss during grunking to be like an
overboost cutoff, when the fuel pump cuts out momentarily (that's a
really hard, hit-a-brick-wall, type of power loss), or more of a miss,
stumble, or hesitation?
George Fairbanks <fairbanks at cmu.edu> wrote:
> Hey guys,
> I'm hoping that one of you can help me diagnose a problem I'm having.
> I've got a trustworthy local mechanic but he's not a 200 expert, nor
> even an Audi specialist.
> A bit of history -- probably three years ago I started the car on a cool
> morning and, for the first time, it put out a puff of smoke out the
> back. Since then the car has had a stinky exhaust when first started
> after sitting but it passes emissions just fine when warmed up. My
> mechanic guessed that some oil was making its way past the turbo and
> being burned off when first started. The car hasn't been using a
> noticeable amount of oil. I've been getting an indicated 1.7 bar of
> boost for a few years now instead of 1.8, but haven't been bothered
> enough to look into fixing that.
> Some of you might know this car as it's Greg Amy's old car. It's been
> running without incident for the past five years here in Pittsburgh
> while I'm working on my phd. It's got 193k miles on it now and I
> believe Greg's had the chip in there since about 100k miles.
> This past weekend I was accelerating hard (honestly, I don't do this
> often as I'm stuck in Pittsburgh, the city of potholes and I have
> cracked one rim here already) and heard a funny noise coincident with a
> dip in power. The noise was sort of like a "grunk". When I restarted
> the car about an hour later (I did let the car cool down before parking)
> the car put out enough whitish smoke to really scare me.
> When the smoke went away after a couple seconds, however, the car ran
> fine for the rest of the day and for the return leg of my road trip (240
> miles). Gas mileage on the trip was normal too, 27 mpg on the highway.
> I have heard this grunk noise a couple times before but had chalked it
> up to mid-grade gas when the chip requires high octane, but was only
> half convinced it was premature detonation. Now I really don't think
> that's it.
> Any ideas on what the problem could be?
> Thanks in advance,
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