Stumblin, bumblin, fumblin, 5KTQ

[Ron Katona]

Appreciate any advice tracking down a bad stumble my '86 5ktq developed
yesterday. This car is my daily driver for a 5-mile commute and has been
for the last six months. Ran fine until yesterday when merging on the
highway under about 3/4 throttle it suddenly stumbled, then began to run
rough. The rough running has continued since then. The basic feel is
that it's running on 4 cylinders... a regular miss rather than a
herky-jerky stumble. It's evident throughout the rev range - power is
obviously down.

About all I could think to check when I got to work was that all the
plug wires are on tight and to look for any obvious loose vacuum lines.
Didn't see anything. Turbo is developing 1.2 bar at full throttle...
normal for this 200,000+ mile car. No big plumes of white or blue smoke
that might indicate a blown gasket or damaged valve. Car has 1/2 tank of
gas on board. Mileage dropped to 12 mpg since then. The car starts and
runs OK considering (no stalling or hard starting).

I'm fairly handy with a wrench on cars, but this is my first Audi and
first turbo car of any kind. Other than maybe pulling the plugs and
replacing them while checking their condition, I don't have much of an
idea where to start troubleshooting on this car... maybe a bad injector?

Any ideas? Any common failures to look for? Troubleshooting tips for the
fuel and ignition systems? Helpful web sites?

Please help, until I get this thing back on the road I'm forced to drive
my '95 M3 to work every day. ;) Thanks in advance!
--
Ron Katona