stubborn rieger / engine problems

[amalventano1@comcast.net (Allyn)]

My string of good luck has ended.
Problem: (noticed increased random missing when hot at idle over past few weeks). Car ran fine, then
sputtered under acceleration (as if one cylinder wasnt firing). During this minute it only missed
under load (revs freely when not loaded, no misses). After ~1 minute the sputtering went away but
there was a noticable (not major) loss of power under load. The loss of power doesnt seem to be from
any one cylinder. Car is still drivable. Revs freely as it ever did with no misses. The next time i
drove it, i had the same power loss, but noticed a sputtering that occurs only when coming off the
throttle (under load). No sputtering occurs under acceleration, only the slight power loss. Engine
coasts down cleanly when off of pedal (no sputtering). The sputter only occurs under partial
throttle and especially when coming off of full throttle. Still no stuttering while free reving.

What was done so far:
Change plugs: no effect (old plugs were clean, all 4 looked identical, no sign of plugs being
cause).
Remove/inspect plug wires: (neuspeed wires), all wires had consistent resistance, even with wires
wet.
Swapped coil with another one: no effect, same exact symptoms.
Checked ignition timing: Dead on, no adjustment necessary.
Checked cam timing: dead on.
*at this point i let the engine idle up to temperature and noted no missing at all, i can only
assume the missing problem was corrected and is not related to the sputtering problem*

Please let me know any opinions/thoughts. My hunch is possibly something fuel related or perhaps
something funky with the coil driver.

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch, driveshafts, wheels :)