Hello,

This may be a rather lengthy explanation, so thanks in advance to anyone who reads it all and has tips!

After months of scouring AutoTrader, Craigslist, eBay Motors, and beyond for a '91 100, I finally found almost that, only more fun: a '92 100/S4. Better yet, it only has 172,000 miles and has been pretty well cared for. I've had it about two weeks now and I'm just head over heels gaga in love with it.

That being said, I want to take real good care of this bad boy and keep it on the road for years to come. I had the folks at Achtuning (I'm in the Seattle area) take a look at it, and was pleased to find that they said it was one of the cleanest, driest engines they'd seen on an Audi that age in years. Not only that, they were drooling over the car. Sweet.

I am having one strange issue that I haven't yet been able to put my finger on. Basically, when I'm cruising along at a fairly constant speed, it will occasionally jolt/jerk/stutter almost like it's coming out of a poorly executed shift. Now, if it was doing that mid-late shift, I would just figure I haven't gotten used to the clutch yet (it's a stage 3, which is new to me but going well), but it does this almost exclusively when my foot is nowhere near the clutch pedal. It seems marginally more likely to do it when I'm in the higher of two possible gears that could be reasonable at a given speed (say, more likely to do it when I'm in 4th at 35mph than if I'm in 3rd) but that could be a coincidence. It also seems ever so slightly more likely to do it if the engine is on the cold side, but again, could be coincidence.

It's similar to this problem, so I will be mentioning these possible remedies to the mechanics, but since I'm not sure if he and I had the same problem, I'll go ahead and solicit whatever other ideas are out there.

Both my coworker at the shop where I work, and the techs at Achtuning noticed that the turbo inlet hose was worn out. There was a dime-sized whole near the end that meets the turbo. Everyone seemed to agree that it needed to be replaced right away, and that would more than likely fix the problem.

Luckily for me, the local dealership had an OEM hose available within a couple days, and my shop replaced it yesterday. Here's where it gets weird. It didn't fix the problem, but it has definitely reduced the frequency of the mystery jolts. So it seems like while the bad hose may have been contributing to the problem, it wasn't the whole problem. Bummer.

A few basic facts about the car in case it helps:
*1992 100/S4 Quattro 2.2L I5
*Manual Transmission (is there any other way to drive?) w/ Stage 3 clutch
*A handful of mods courtesy of the previous owner:
-----3" straight pipe Magnaflow exhaust
-----044 Bosch fuel pump & 034 fuel pressure regulator
-----ECU chip (I don't know much about how it's been tuned, just that it has been)
-----Front mounted intercooler
-----Vacuum brake booster
-----H&R Springs and updated suspension
*Spark plugs, spark plug connector, and timing belt all replaced recently by previous owner

So anyway, the million dollar question is: if the bad turbo inlet hose wasn't the real problem, what is? My greatest fear at this point is a transmission problem, although that seems unlikely given the mileage and the relative longevity of the M/T. It's just always on my mind, since that's what totaled my first ever car. At this point I figure it could be anything from O2 sensors to fuel line problems to an issue with the tuning to...?

Whatever it is, I want to fix it right away. The jerking scares the bejeesus out of me, and like I said, I want to keep this baby shipshape for a long time. Any and all feedback welcome. Thanks in advance, and glad to be here!