Hi Doug,
Converted your fuel consumption to mileage 1000 km / 50 lit = 46.9 mpg. What was you avg speed?
I converted the range during which your slowdown shudder was observed 30-35 kkm = 18.6-21.7 kmi. I felt it right about there too.
I can't figure out why you do not feel the highspeed shudder in fifth gear, light throttle, 2400-2500 rpm, 116-121 kmph, 72-75 mph if you are feeling it in lower gears. Why are you not upshifting at 3200 with a light throttle if you are not in top gear? I tried your style first thing this morning, ambient temp 20* F, -7* C, cold engine, 3rd gear, 2500 rpm, and set the cruise control on a level boulevard ... Shudder-city! When the engine is cold I get a distinctly louder diesel clatter when applying a light throttle and no clatter when coasting under no throttle. The power demands from the cruise control was intermittent, so the clatter was going on-and-off and each time the floor pan was jumping around like a ... like a ... hmmmmmm ... like an orgasm on the mogul slope? Turned off the cruise and did it again using light throttle. Did it in fourth gear too. OK, here's my latest theory: High speed shudder is a type of control overshoot or hysteresis which occurs when the engine torque pushes the car to a speed higher than what the ECM believes is correct for the current throttle position, causing it to cut the fuel flow, slowing the car to a speed that is below what the ECM believes is correct for the current throttle position. And so on ...
Speaking of sudden fuel cutoff, when you use cruise control and you squeeze the accelerate switch does it take about 2 seconds before it takes effect like a rocket (compressing the springs in the seatback), and when you release the accelerate switch does it chop off the fuel supply so fast the springs in the seatback throw you forward? Reeeeeeeal refined
Do you have to press the coast button for about 5-7 seconds before the fuel supply is overly geeeeeeently tapered off? You call that refined or unsafe?
I usually give a slight touch on the clutch pedal and then hit the coast button. Do all A4 TDI cruise controls work like this?
Dr. Dotgain
2000 Golf GL TDI 5-speed one-year-old 28,000 miles (45,000 km)