V6 Pinging right between coasting and acceleration

I have 1995 Audi 90 with the 12V V6. I bought the car used 4 years ago and I haven't been able to diagnose this problem yet.
The problem appears mostly in highway driving on level road. The valves
seem to be very happy to just clatter and ping away at just the exact throttle required to just maintain my speed. It seems most noticable above 60mph and seems worse at higher speeds. Just a hint more throttle to give an almost inperceivable acceleration and it very quickly and sharply get worse and then stops pinging.....until the car speed catches up with the throttle again and guess what, pinging. The same happens with just a hint less throttle. Again, with an almost inpercievable decelleration and the pinging stops....until the car slows to the throttle. This is all within fractions of 1mph. But, it's loud enough and disturbing enough that I'm always having to adjust the throttle away from a constant speed, just a whisper, to keep the valves from clattering away.
If I crest a hill, just as the engine load changes from pulling up the hill to coasting down the other side the pinging appears.
If "crest" a dip, same deal. As I go from coasting to pulling up the next hill the pinging appears.
Are the knock sensors suppose to alert the CPU to this and correct it? Could it be a bad knock sensor?... or would it be worse?
Any suggestions?
Gene
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Are you that sure it's valves? Because your symptoms sound suspiciously "on-boost" - and if the turbo is knackered maybe you're just hearing it's death rattle...
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[Snip]

Err... what turbo?
--
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')

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Yea. Trust me, there's no turbo. :-(
wrote:

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Sorry, totally missed it...
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Some of the V6s had problems with the timing belt tensioners. Not sure if yours is one of them but this causes rattling sounds.
Tony '91 100Q 5spd Son's 98 2.8 30V A4
Gene wrote:

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Make sure you're using high-Octane gas.
JP

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Or alternatively, retard the timing a degree or two. Though that will have performance consequences.
Cheers,
C
JP Roberts wrote:

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I am using 92 or 93 octane, nothing but.
Adjust the valve timing? There's no way to retard the ignition timing that I know of.
Gene

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Yup. You're hearing something else. The earliest Audis to actually have any *power* (and yours is in this vintage - the late '80s turbos, 20 valves, and early '90s V6, etc.) tended to beat up the splines on the output shaft from the gearbox. The resulting looseness produces noises.
It *starts out* sounding exactly like detonation (pinging), but if you think about it, it occurs at precisely the wrong times. Detonation occurs under engine *load* and this doesn't.
It is definitely not the valves because it comes and goes so quickly. Valve clatter is constant over a wide rpm range (although it can go away when the engine warms up if the clearances are small) because the clearances don't change that quickly nor, in the case of hydraulic lifters, do they pump up and empty that quickly.
You're left with this looseness in the driveline as your only probable cause, and the symptomatic sounds match the theory exactly - when the driveline is vascillating slightly between acceleration and deceleration. It gets progressively worse, depending on how much stress is put on the joint, but it does so fairly slowly and even when it's making quite alarming noises, it doesn't really keep the car from being driven. It's mostly embarassment. Contact Jim at Blaufergngen (www.audiquattroparts.com) and ask about his repair parts kit. -- C.R. Krieger (Been there; done that)
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warp2 snipped-for-privacy@yahoo.com (C.R. Krieger) wrote:

Something grates everytime I see this - surely it should be Blauvergngen?
--
Peter Bell (Note Spamtrap - To reply, replace 'invalid' with 'bellfamily')

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(C.R. Krieger) wrote:

Sorry; he spells it this way. As a born-&-raised Wisconsin boy, his German spelling and grammar isn't very good; but it *is* a made-up word, after all. -- C.R. Krieger "Ignore 'em, m'dear; they're beneath our dignity." - W.C. Fields
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Wow this thread is still on a server?! Anyway I fixed the pinging....and yes, it really was pinging, not drive-train noise.
I pulled the heads and replaced valve guides and all the gaskets. The pinging I detailed in this thread is now completely gone, replaced by much better highway accelleration. I'm guessing that oil being sucked past the valve guides was fooling the O2 sensors into thinking the mixture was rich. Also, the valves may have been clattering around a little in loose guides.
Gene
(C.R. Krieger) wrote:

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