[16v] hard start, bucking/bogging off idle

[treed2 at wsu.edu (T. Reed)]

Well, my Scirocco finally realized that winter is here and it's time to 
start behaving erratically.

She was running like a honduh owner to a stack of free decals, up until 
I put the snow tires on. Suddenly, things have gone to crap.

When I get in and turn the key, the engine spins over at normal speed, 
About every sixth or so 'wuh' in the wuh-wuh-wuh-wuh cranking noise is 
followed by a single firing of the engine. But it takes 1 to 3 sets of 
fifteen to twenty wuh-wuh-wuh's before it will fire twice in a row, and 
start. After that, it seems to idle fine.

No battery problems are apparent; lights dim when cranking but no more 
than they always have. The torch-soldered 4 gauge underhood wiring and 
grounds are 3 months old. Battery is also only 3 months old. Engine seems 
to crank at normal speed.

Plug wires seem to be seated fine in the valve cover and on the dist. Hall 
sender and dist are relatively new (~3-4 years old now), the wiring looked 
okay in a visual inspection, coolant temp sender wire hooked up. That's 
all I checked because its 23 F outside and windy.

Anyway, after it gets started, it does this thing while coming off idle. 
Sometimes, when you step on the gas, it will sound like its trying to 
drive straight up a wall (the engine sounds very loaded down), then if 
you let off the gas it returns to normal and it will usually go if you 
step on the gas again (although 1 in 10 times it will die instead).

If you just keep your foot on the gas instead of letting off, it will 
typically recover in about 3 to 5 seconds and kind of buck a little, 
sometimes with a little pop noise (not quite a backfire; it might even be 
the motor rocking in its mounts), then accelerate like crap as if it had 
lost a cylinder or two. Letting off the gas and "trying again" seems to 
alleviate the problem 90% of the time.

I thought at first that it might be due to bad gas from filling up at a 
different gas station than I usually do (or maybe I put 87 in by 
accident). I filled up with Chevron 92 after running it down to 1/8 tank 
or so. It bucked again on the way out of the gas station (expected since 
the old gas was still in the fuel lines), but seemed to run a lot better 
for a while after that. Didn't have the problem at about 8 or 9 
stoplights in a row, so I figured it was gone. But I guess I was wrong, 
because its been happening again, although less frequently and with less 
vigor.

When cruising at high RPMs the car behaves pretty much normally, except 
about 5% of the time when I mash the gas to pass somebody, it bogs for a 
fraction of a second then recovers immediately. Otherwise, normal 
acceleration, etc.


So... who's had this problem before? :)

Where should I look first..? It's too cold to go out there and blindly 
poke around. :)

Thanks

-Toby


BTW this is a 2l 16v with vanilla cis-e